(function(f){if(typeof exports==="object"&&typeof module!=="undefined"){module.exports=f()}else if(typeof define==="function"&&define.amd){define([],f)}else{var g;if(typeof window!=="undefined"){g=window}else if(typeof global!=="undefined"){g=global}else if(typeof self!=="undefined"){g=self}else{g=this}g.chai = f()}})(function(){var define,module,exports;return (function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);var f=new Error("Cannot find module '"+o+"'");throw f.code="MODULE_NOT_FOUND",f}var l=n[o]={exports:{}};t[o][0].call(l.exports,function(e){var n=t[o][1][e];return s(n?n:e)},l,l.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s})({1:[function(require,module,exports){
  module.exports = require('./lib/chai');

  },{"./lib/chai":2}],2:[function(require,module,exports){
  /*!
   * chai
   * Copyright(c) 2011-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  var used = [];

  /*!
   * Chai version
   */

  exports.version = '4.1.2';

  /*!
   * Assertion Error
   */

  exports.AssertionError = require('assertion-error');

  /*!
   * Utils for plugins (not exported)
   */

  var util = require('./chai/utils');

  /**
   * # .use(function)
   *
   * Provides a way to extend the internals of Chai.
   *
   * @param {Function}
   * @returns {this} for chaining
   * @api public
   */

  exports.use = function (fn) {
    if (!~used.indexOf(fn)) {
      fn(exports, util);
      used.push(fn);
    }

    return exports;
  };

  /*!
   * Utility Functions
   */

  exports.util = util;

  /*!
   * Configuration
   */

  var config = require('./chai/config');
  exports.config = config;

  /*!
   * Primary `Assertion` prototype
   */

  var assertion = require('./chai/assertion');
  exports.use(assertion);

  /*!
   * Core Assertions
   */

  var core = require('./chai/core/assertions');
  exports.use(core);

  /*!
   * Expect interface
   */

  var expect = require('./chai/interface/expect');
  exports.use(expect);

  /*!
   * Should interface
   */

  var should = require('./chai/interface/should');
  exports.use(should);

  /*!
   * Assert interface
   */

  var assert = require('./chai/interface/assert');
  exports.use(assert);

  },{"./chai/assertion":3,"./chai/config":4,"./chai/core/assertions":5,"./chai/interface/assert":6,"./chai/interface/expect":7,"./chai/interface/should":8,"./chai/utils":22,"assertion-error":33}],3:[function(require,module,exports){
  /*!
   * chai
   * http://chaijs.com
   * Copyright(c) 2011-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  var config = require('./config');

  module.exports = function (_chai, util) {
    /*!
     * Module dependencies.
     */

    var AssertionError = _chai.AssertionError
      , flag = util.flag;

    /*!
     * Module export.
     */

    _chai.Assertion = Assertion;

    /*!
     * Assertion Constructor
     *
     * Creates object for chaining.
     *
     * `Assertion` objects contain metadata in the form of flags. Three flags can
     * be assigned during instantiation by passing arguments to this constructor:
     *
     * - `object`: This flag contains the target of the assertion. For example, in
     *   the assertion `expect(numKittens).to.equal(7);`, the `object` flag will
     *   contain `numKittens` so that the `equal` assertion can reference it when
     *   needed.
     *
     * - `message`: This flag contains an optional custom error message to be
     *   prepended to the error message that's generated by the assertion when it
     *   fails.
     *
     * - `ssfi`: This flag stands for "start stack function indicator". It
     *   contains a function reference that serves as the starting point for
     *   removing frames from the stack trace of the error that's created by the
     *   assertion when it fails. The goal is to provide a cleaner stack trace to
     *   end users by removing Chai's internal functions. Note that it only works
     *   in environments that support `Error.captureStackTrace`, and only when
     *   `Chai.config.includeStack` hasn't been set to `false`.
     *
     * - `lockSsfi`: This flag controls whether or not the given `ssfi` flag
     *   should retain its current value, even as assertions are chained off of
     *   this object. This is usually set to `true` when creating a new assertion
     *   from within another assertion. It's also temporarily set to `true` before
     *   an overwritten assertion gets called by the overwriting assertion.
     *
     * @param {Mixed} obj target of the assertion
     * @param {String} msg (optional) custom error message
     * @param {Function} ssfi (optional) starting point for removing stack frames
     * @param {Boolean} lockSsfi (optional) whether or not the ssfi flag is locked
     * @api private
     */

    function Assertion (obj, msg, ssfi, lockSsfi) {
      flag(this, 'ssfi', ssfi || Assertion);
      flag(this, 'lockSsfi', lockSsfi);
      flag(this, 'object', obj);
      flag(this, 'message', msg);

      return util.proxify(this);
    }

    Object.defineProperty(Assertion, 'includeStack', {
      get: function() {
        console.warn('Assertion.includeStack is deprecated, use chai.config.includeStack instead.');
        return config.includeStack;
      },
      set: function(value) {
        console.warn('Assertion.includeStack is deprecated, use chai.config.includeStack instead.');
        config.includeStack = value;
      }
    });

    Object.defineProperty(Assertion, 'showDiff', {
      get: function() {
        console.warn('Assertion.showDiff is deprecated, use chai.config.showDiff instead.');
        return config.showDiff;
      },
      set: function(value) {
        console.warn('Assertion.showDiff is deprecated, use chai.config.showDiff instead.');
        config.showDiff = value;
      }
    });

    Assertion.addProperty = function (name, fn) {
      util.addProperty(this.prototype, name, fn);
    };

    Assertion.addMethod = function (name, fn) {
      util.addMethod(this.prototype, name, fn);
    };

    Assertion.addChainableMethod = function (name, fn, chainingBehavior) {
      util.addChainableMethod(this.prototype, name, fn, chainingBehavior);
    };

    Assertion.overwriteProperty = function (name, fn) {
      util.overwriteProperty(this.prototype, name, fn);
    };

    Assertion.overwriteMethod = function (name, fn) {
      util.overwriteMethod(this.prototype, name, fn);
    };

    Assertion.overwriteChainableMethod = function (name, fn, chainingBehavior) {
      util.overwriteChainableMethod(this.prototype, name, fn, chainingBehavior);
    };

    /**
     * ### .assert(expression, message, negateMessage, expected, actual, showDiff)
     *
     * Executes an expression and check expectations. Throws AssertionError for reporting if test doesn't pass.
     *
     * @name assert
     * @param {Philosophical} expression to be tested
     * @param {String|Function} message or function that returns message to display if expression fails
     * @param {String|Function} negatedMessage or function that returns negatedMessage to display if negated expression fails
     * @param {Mixed} expected value (remember to check for negation)
     * @param {Mixed} actual (optional) will default to `this.obj`
     * @param {Boolean} showDiff (optional) when set to `true`, assert will display a diff in addition to the message if expression fails
     * @api private
     */

    Assertion.prototype.assert = function (expr, msg, negateMsg, expected, _actual, showDiff) {
      var ok = util.test(this, arguments);
      if (false !== showDiff) showDiff = true;
      if (undefined === expected && undefined === _actual) showDiff = false;
      if (true !== config.showDiff) showDiff = false;

      if (!ok) {
        msg = util.getMessage(this, arguments);
        var actual = util.getActual(this, arguments);
        throw new AssertionError(msg, {
            actual: actual
          , expected: expected
          , showDiff: showDiff
        }, (config.includeStack) ? this.assert : flag(this, 'ssfi'));
      }
    };

    /*!
     * ### ._obj
     *
     * Quick reference to stored `actual` value for plugin developers.
     *
     * @api private
     */

    Object.defineProperty(Assertion.prototype, '_obj',
      { get: function () {
          return flag(this, 'object');
        }
      , set: function (val) {
          flag(this, 'object', val);
        }
    });
  };

  },{"./config":4}],4:[function(require,module,exports){
  module.exports = {

    /**
     * ### config.includeStack
     *
     * User configurable property, influences whether stack trace
     * is included in Assertion error message. Default of false
     * suppresses stack trace in the error message.
     *
     *     chai.config.includeStack = true;  // enable stack on error
     *
     * @param {Boolean}
     * @api public
     */

    includeStack: false,

    /**
     * ### config.showDiff
     *
     * User configurable property, influences whether or not
     * the `showDiff` flag should be included in the thrown
     * AssertionErrors. `false` will always be `false`; `true`
     * will be true when the assertion has requested a diff
     * be shown.
     *
     * @param {Boolean}
     * @api public
     */

    showDiff: true,

    /**
     * ### config.truncateThreshold
     *
     * User configurable property, sets length threshold for actual and
     * expected values in assertion errors. If this threshold is exceeded, for
     * example for large data structures, the value is replaced with something
     * like `[ Array(3) ]` or `{ Object (prop1, prop2) }`.
     *
     * Set it to zero if you want to disable truncating altogether.
     *
     * This is especially userful when doing assertions on arrays: having this
     * set to a reasonable large value makes the failure messages readily
     * inspectable.
     *
     *     chai.config.truncateThreshold = 0;  // disable truncating
     *
     * @param {Number}
     * @api public
     */

    truncateThreshold: 40,

    /**
     * ### config.useProxy
     *
     * User configurable property, defines if chai will use a Proxy to throw
     * an error when a non-existent property is read, which protects users
     * from typos when using property-based assertions.
     *
     * Set it to false if you want to disable this feature.
     *
     *     chai.config.useProxy = false;  // disable use of Proxy
     *
     * This feature is automatically disabled regardless of this config value
     * in environments that don't support proxies.
     *
     * @param {Boolean}
     * @api public
     */

    useProxy: true,

    /**
     * ### config.proxyExcludedKeys
     *
     * User configurable property, defines which properties should be ignored
     * instead of throwing an error if they do not exist on the assertion.
     * This is only applied if the environment Chai is running in supports proxies and
     * if the `useProxy` configuration setting is enabled.
     * By default, `then` and `inspect` will not throw an error if they do not exist on the
     * assertion object because the `.inspect` property is read by `util.inspect` (for example, when
     * using `console.log` on the assertion object) and `.then` is necessary for promise type-checking.
     *
     *     // By default these keys will not throw an error if they do not exist on the assertion object
     *     chai.config.proxyExcludedKeys = ['then', 'inspect'];
     *
     * @param {Array}
     * @api public
     */

    proxyExcludedKeys: ['then', 'inspect', 'toJSON']
  };

  },{}],5:[function(require,module,exports){
  /*!
   * chai
   * http://chaijs.com
   * Copyright(c) 2011-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  module.exports = function (chai, _) {
    var Assertion = chai.Assertion
      , AssertionError = chai.AssertionError
      , flag = _.flag;

    /**
     * ### Language Chains
     *
     * The following are provided as chainable getters to improve the readability
     * of your assertions.
     *
     * **Chains**
     *
     * - to
     * - be
     * - been
     * - is
     * - that
     * - which
     * - and
     * - has
     * - have
     * - with
     * - at
     * - of
     * - same
     * - but
     * - does
     *
     * @name language chains
     * @namespace BDD
     * @api public
     */

    [ 'to', 'be', 'been'
    , 'is', 'and', 'has', 'have'
    , 'with', 'that', 'which', 'at'
    , 'of', 'same', 'but', 'does' ].forEach(function (chain) {
      Assertion.addProperty(chain);
    });

    /**
     * ### .not
     *
     * Negates all assertions that follow in the chain.
     *
     *     expect(function () {}).to.not.throw();
     *     expect({a: 1}).to.not.have.property('b');
     *     expect([1, 2]).to.be.an('array').that.does.not.include(3);
     *
     * Just because you can negate any assertion with `.not` doesn't mean you
     * should. With great power comes great responsibility. It's often best to
     * assert that the one expected output was produced, rather than asserting
     * that one of countless unexpected outputs wasn't produced. See individual
     * assertions for specific guidance.
     *
     *     expect(2).to.equal(2); // Recommended
     *     expect(2).to.not.equal(1); // Not recommended
     *
     * @name not
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('not', function () {
      flag(this, 'negate', true);
    });

    /**
     * ### .deep
     *
     * Causes all `.equal`, `.include`, `.members`, `.keys`, and `.property`
     * assertions that follow in the chain to use deep equality instead of strict
     * (`===`) equality. See the `deep-eql` project page for info on the deep
     * equality algorithm: https://github.com/chaijs/deep-eql.
     *
     *     // Target object deeply (but not strictly) equals `{a: 1}`
     *     expect({a: 1}).to.deep.equal({a: 1});
     *     expect({a: 1}).to.not.equal({a: 1});
     *
     *     // Target array deeply (but not strictly) includes `{a: 1}`
     *     expect([{a: 1}]).to.deep.include({a: 1});
     *     expect([{a: 1}]).to.not.include({a: 1});
     *
     *     // Target object deeply (but not strictly) includes `x: {a: 1}`
     *     expect({x: {a: 1}}).to.deep.include({x: {a: 1}});
     *     expect({x: {a: 1}}).to.not.include({x: {a: 1}});
     *
     *     // Target array deeply (but not strictly) has member `{a: 1}`
     *     expect([{a: 1}]).to.have.deep.members([{a: 1}]);
     *     expect([{a: 1}]).to.not.have.members([{a: 1}]);
     *
     *     // Target set deeply (but not strictly) has key `{a: 1}`
     *     expect(new Set([{a: 1}])).to.have.deep.keys([{a: 1}]);
     *     expect(new Set([{a: 1}])).to.not.have.keys([{a: 1}]);
     *
     *     // Target object deeply (but not strictly) has property `x: {a: 1}`
     *     expect({x: {a: 1}}).to.have.deep.property('x', {a: 1});
     *     expect({x: {a: 1}}).to.not.have.property('x', {a: 1});
     *
     * @name deep
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('deep', function () {
      flag(this, 'deep', true);
    });

    /**
     * ### .nested
     *
     * Enables dot- and bracket-notation in all `.property` and `.include`
     * assertions that follow in the chain.
     *
     *     expect({a: {b: ['x', 'y']}}).to.have.nested.property('a.b[1]');
     *     expect({a: {b: ['x', 'y']}}).to.nested.include({'a.b[1]': 'y'});
     *
     * If `.` or `[]` are part of an actual property name, they can be escaped by
     * adding two backslashes before them.
     *
     *     expect({'.a': {'[b]': 'x'}}).to.have.nested.property('\\.a.\\[b\\]');
     *     expect({'.a': {'[b]': 'x'}}).to.nested.include({'\\.a.\\[b\\]': 'x'});
     *
     * `.nested` cannot be combined with `.own`.
     *
     * @name nested
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('nested', function () {
      flag(this, 'nested', true);
    });

    /**
     * ### .own
     *
     * Causes all `.property` and `.include` assertions that follow in the chain
     * to ignore inherited properties.
     *
     *     Object.prototype.b = 2;
     *
     *     expect({a: 1}).to.have.own.property('a');
     *     expect({a: 1}).to.have.property('b').but.not.own.property('b');
     *
     *     expect({a: 1}).to.own.include({a: 1});
     *     expect({a: 1}).to.include({b: 2}).but.not.own.include({b: 2});
     *
     * `.own` cannot be combined with `.nested`.
     *
     * @name own
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('own', function () {
      flag(this, 'own', true);
    });

    /**
     * ### .ordered
     *
     * Causes all `.members` assertions that follow in the chain to require that
     * members be in the same order.
     *
     *     expect([1, 2]).to.have.ordered.members([1, 2])
     *       .but.not.have.ordered.members([2, 1]);
     *
     * When `.include` and `.ordered` are combined, the ordering begins at the
     * start of both arrays.
     *
     *     expect([1, 2, 3]).to.include.ordered.members([1, 2])
     *       .but.not.include.ordered.members([2, 3]);
     *
     * @name ordered
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('ordered', function () {
      flag(this, 'ordered', true);
    });

    /**
     * ### .any
     *
     * Causes all `.keys` assertions that follow in the chain to only require that
     * the target have at least one of the given keys. This is the opposite of
     * `.all`, which requires that the target have all of the given keys.
     *
     *     expect({a: 1, b: 2}).to.not.have.any.keys('c', 'd');
     *
     * See the `.keys` doc for guidance on when to use `.any` or `.all`.
     *
     * @name any
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('any', function () {
      flag(this, 'any', true);
      flag(this, 'all', false);
    });


    /**
     * ### .all
     *
     * Causes all `.keys` assertions that follow in the chain to require that the
     * target have all of the given keys. This is the opposite of `.any`, which
     * only requires that the target have at least one of the given keys.
     *
     *     expect({a: 1, b: 2}).to.have.all.keys('a', 'b');
     *
     * Note that `.all` is used by default when neither `.all` nor `.any` are
     * added earlier in the chain. However, it's often best to add `.all` anyway
     * because it improves readability.
     *
     * See the `.keys` doc for guidance on when to use `.any` or `.all`.
     *
     * @name all
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('all', function () {
      flag(this, 'all', true);
      flag(this, 'any', false);
    });

    /**
     * ### .a(type[, msg])
     *
     * Asserts that the target's type is equal to the given string `type`. Types
     * are case insensitive. See the `type-detect` project page for info on the
     * type detection algorithm: https://github.com/chaijs/type-detect.
     *
     *     expect('foo').to.be.a('string');
     *     expect({a: 1}).to.be.an('object');
     *     expect(null).to.be.a('null');
     *     expect(undefined).to.be.an('undefined');
     *     expect(new Error).to.be.an('error');
     *     expect(Promise.resolve()).to.be.a('promise');
     *     expect(new Float32Array).to.be.a('float32array');
     *     expect(Symbol()).to.be.a('symbol');
     *
     * `.a` supports objects that have a custom type set via `Symbol.toStringTag`.
     *
     *     var myObj = {
     *       [Symbol.toStringTag]: 'myCustomType'
     *     };
     *
     *     expect(myObj).to.be.a('myCustomType').but.not.an('object');
     *
     * It's often best to use `.a` to check a target's type before making more
     * assertions on the same target. That way, you avoid unexpected behavior from
     * any assertion that does different things based on the target's type.
     *
     *     expect([1, 2, 3]).to.be.an('array').that.includes(2);
     *     expect([]).to.be.an('array').that.is.empty;
     *
     * Add `.not` earlier in the chain to negate `.a`. However, it's often best to
     * assert that the target is the expected type, rather than asserting that it
     * isn't one of many unexpected types.
     *
     *     expect('foo').to.be.a('string'); // Recommended
     *     expect('foo').to.not.be.an('array'); // Not recommended
     *
     * `.a` accepts an optional `msg` argument which is a custom error message to
     * show when the assertion fails. The message can also be given as the second
     * argument to `expect`.
     *
     *     expect(1).to.be.a('string', 'nooo why fail??');
     *     expect(1, 'nooo why fail??').to.be.a('string');
     *
     * `.a` can also be used as a language chain to improve the readability of
     * your assertions.
     *
     *     expect({b: 2}).to.have.a.property('b');
     *
     * The alias `.an` can be used interchangeably with `.a`.
     *
     * @name a
     * @alias an
     * @param {String} type
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    function an (type, msg) {
      if (msg) flag(this, 'message', msg);
      type = type.toLowerCase();
      var obj = flag(this, 'object')
        , article = ~[ 'a', 'e', 'i', 'o', 'u' ].indexOf(type.charAt(0)) ? 'an ' : 'a ';

      this.assert(
          type === _.type(obj).toLowerCase()
        , 'expected #{this} to be ' + article + type
        , 'expected #{this} not to be ' + article + type
      );
    }

    Assertion.addChainableMethod('an', an);
    Assertion.addChainableMethod('a', an);

    /**
     * ### .include(val[, msg])
     *
     * When the target is a string, `.include` asserts that the given string `val`
     * is a substring of the target.
     *
     *     expect('foobar').to.include('foo');
     *
     * When the target is an array, `.include` asserts that the given `val` is a
     * member of the target.
     *
     *     expect([1, 2, 3]).to.include(2);
     *
     * When the target is an object, `.include` asserts that the given object
     * `val`'s properties are a subset of the target's properties.
     *
     *     expect({a: 1, b: 2, c: 3}).to.include({a: 1, b: 2});
     *
     * When the target is a Set or WeakSet, `.include` asserts that the given `val` is a
     * member of the target. SameValueZero equality algorithm is used.
     *
     *     expect(new Set([1, 2])).to.include(2);
     *
     * When the target is a Map, `.include` asserts that the given `val` is one of
     * the values of the target. SameValueZero equality algorithm is used.
     *
     *     expect(new Map([['a', 1], ['b', 2]])).to.include(2);
     *
     * Because `.include` does different things based on the target's type, it's
     * important to check the target's type before using `.include`. See the `.a`
     * doc for info on testing a target's type.
     *
     *     expect([1, 2, 3]).to.be.an('array').that.includes(2);
     *
     * By default, strict (`===`) equality is used to compare array members and
     * object properties. Add `.deep` earlier in the chain to use deep equality
     * instead (WeakSet targets are not supported). See the `deep-eql` project
     * page for info on the deep equality algorithm: https://github.com/chaijs/deep-eql.
     *
     *     // Target array deeply (but not strictly) includes `{a: 1}`
     *     expect([{a: 1}]).to.deep.include({a: 1});
     *     expect([{a: 1}]).to.not.include({a: 1});
     *
     *     // Target object deeply (but not strictly) includes `x: {a: 1}`
     *     expect({x: {a: 1}}).to.deep.include({x: {a: 1}});
     *     expect({x: {a: 1}}).to.not.include({x: {a: 1}});
     *
     * By default, all of the target's properties are searched when working with
     * objects. This includes properties that are inherited and/or non-enumerable.
     * Add `.own` earlier in the chain to exclude the target's inherited
     * properties from the search.
     *
     *     Object.prototype.b = 2;
     *
     *     expect({a: 1}).to.own.include({a: 1});
     *     expect({a: 1}).to.include({b: 2}).but.not.own.include({b: 2});
     *
     * Note that a target object is always only searched for `val`'s own
     * enumerable properties.
     *
     * `.deep` and `.own` can be combined.
     *
     *     expect({a: {b: 2}}).to.deep.own.include({a: {b: 2}});
     *
     * Add `.nested` earlier in the chain to enable dot- and bracket-notation when
     * referencing nested properties.
     *
     *     expect({a: {b: ['x', 'y']}}).to.nested.include({'a.b[1]': 'y'});
     *
     * If `.` or `[]` are part of an actual property name, they can be escaped by
     * adding two backslashes before them.
     *
     *     expect({'.a': {'[b]': 2}}).to.nested.include({'\\.a.\\[b\\]': 2});
     *
     * `.deep` and `.nested` can be combined.
     *
     *     expect({a: {b: [{c: 3}]}}).to.deep.nested.include({'a.b[0]': {c: 3}});
     *
     * `.own` and `.nested` cannot be combined.
     *
     * Add `.not` earlier in the chain to negate `.include`.
     *
     *     expect('foobar').to.not.include('taco');
     *     expect([1, 2, 3]).to.not.include(4);
     *
     * However, it's dangerous to negate `.include` when the target is an object.
     * The problem is that it creates uncertain expectations by asserting that the
     * target object doesn't have all of `val`'s key/value pairs but may or may
     * not have some of them. It's often best to identify the exact output that's
     * expected, and then write an assertion that only accepts that exact output.
     *
     * When the target object isn't even expected to have `val`'s keys, it's
     * often best to assert exactly that.
     *
     *     expect({c: 3}).to.not.have.any.keys('a', 'b'); // Recommended
     *     expect({c: 3}).to.not.include({a: 1, b: 2}); // Not recommended
     *
     * When the target object is expected to have `val`'s keys, it's often best to
     * assert that each of the properties has its expected value, rather than
     * asserting that each property doesn't have one of many unexpected values.
     *
     *     expect({a: 3, b: 4}).to.include({a: 3, b: 4}); // Recommended
     *     expect({a: 3, b: 4}).to.not.include({a: 1, b: 2}); // Not recommended
     *
     * `.include` accepts an optional `msg` argument which is a custom error
     * message to show when the assertion fails. The message can also be given as
     * the second argument to `expect`.
     *
     *     expect([1, 2, 3]).to.include(4, 'nooo why fail??');
     *     expect([1, 2, 3], 'nooo why fail??').to.include(4);
     *
     * `.include` can also be used as a language chain, causing all `.members` and
     * `.keys` assertions that follow in the chain to require the target to be a
     * superset of the expected set, rather than an identical set. Note that
     * `.members` ignores duplicates in the subset when `.include` is added.
     *
     *     // Target object's keys are a superset of ['a', 'b'] but not identical
     *     expect({a: 1, b: 2, c: 3}).to.include.all.keys('a', 'b');
     *     expect({a: 1, b: 2, c: 3}).to.not.have.all.keys('a', 'b');
     *
     *     // Target array is a superset of [1, 2] but not identical
     *     expect([1, 2, 3]).to.include.members([1, 2]);
     *     expect([1, 2, 3]).to.not.have.members([1, 2]);
     *
     *     // Duplicates in the subset are ignored
     *     expect([1, 2, 3]).to.include.members([1, 2, 2, 2]);
     *
     * Note that adding `.any` earlier in the chain causes the `.keys` assertion
     * to ignore `.include`.
     *
     *     // Both assertions are identical
     *     expect({a: 1}).to.include.any.keys('a', 'b');
     *     expect({a: 1}).to.have.any.keys('a', 'b');
     *
     * The aliases `.includes`, `.contain`, and `.contains` can be used
     * interchangeably with `.include`.
     *
     * @name include
     * @alias contain
     * @alias includes
     * @alias contains
     * @param {Mixed} val
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    function SameValueZero(a, b) {
      return (_.isNaN(a) && _.isNaN(b)) || a === b;
    }

    function includeChainingBehavior () {
      flag(this, 'contains', true);
    }

    function include (val, msg) {
      if (msg) flag(this, 'message', msg);

      var obj = flag(this, 'object')
        , objType = _.type(obj).toLowerCase()
        , flagMsg = flag(this, 'message')
        , negate = flag(this, 'negate')
        , ssfi = flag(this, 'ssfi')
        , isDeep = flag(this, 'deep')
        , descriptor = isDeep ? 'deep ' : '';

      flagMsg = flagMsg ? flagMsg + ': ' : '';

      var included = false;

      switch (objType) {
        case 'string':
          included = obj.indexOf(val) !== -1;
          break;

        case 'weakset':
          if (isDeep) {
            throw new AssertionError(
              flagMsg + 'unable to use .deep.include with WeakSet',
              undefined,
              ssfi
            );
          }

          included = obj.has(val);
          break;

        case 'map':
          var isEql = isDeep ? _.eql : SameValueZero;
          obj.forEach(function (item) {
            included = included || isEql(item, val);
          });
          break;

        case 'set':
          if (isDeep) {
            obj.forEach(function (item) {
              included = included || _.eql(item, val);
            });
          } else {
            included = obj.has(val);
          }
          break;

        case 'array':
          if (isDeep) {
            included = obj.some(function (item) {
              return _.eql(item, val);
            })
          } else {
            included = obj.indexOf(val) !== -1;
          }
          break;

        default:
          // This block is for asserting a subset of properties in an object.
          // `_.expectTypes` isn't used here because `.include` should work with
          // objects with a custom `@@toStringTag`.
          if (val !== Object(val)) {
            throw new AssertionError(
              flagMsg + 'object tested must be an array, a map, an object,'
                + ' a set, a string, or a weakset, but ' + objType + ' given',
              undefined,
              ssfi
            );
          }

          var props = Object.keys(val)
            , firstErr = null
            , numErrs = 0;

          props.forEach(function (prop) {
            var propAssertion = new Assertion(obj);
            _.transferFlags(this, propAssertion, true);
            flag(propAssertion, 'lockSsfi', true);

            if (!negate || props.length === 1) {
              propAssertion.property(prop, val[prop]);
              return;
            }

            try {
              propAssertion.property(prop, val[prop]);
            } catch (err) {
              if (!_.checkError.compatibleConstructor(err, AssertionError)) {
                throw err;
              }
              if (firstErr === null) firstErr = err;
              numErrs++;
            }
          }, this);

          // When validating .not.include with multiple properties, we only want
          // to throw an assertion error if all of the properties are included,
          // in which case we throw the first property assertion error that we
          // encountered.
          if (negate && props.length > 1 && numErrs === props.length) {
            throw firstErr;
          }
          return;
      }

      // Assert inclusion in collection or substring in a string.
      this.assert(
        included
        , 'expected #{this} to ' + descriptor + 'include ' + _.inspect(val)
        , 'expected #{this} to not ' + descriptor + 'include ' + _.inspect(val));
    }

    Assertion.addChainableMethod('include', include, includeChainingBehavior);
    Assertion.addChainableMethod('contain', include, includeChainingBehavior);
    Assertion.addChainableMethod('contains', include, includeChainingBehavior);
    Assertion.addChainableMethod('includes', include, includeChainingBehavior);

    /**
     * ### .ok
     *
     * Asserts that the target is loosely (`==`) equal to `true`. However, it's
     * often best to assert that the target is strictly (`===`) or deeply equal to
     * its expected value.
     *
     *     expect(1).to.equal(1); // Recommended
     *     expect(1).to.be.ok; // Not recommended
     *
     *     expect(true).to.be.true; // Recommended
     *     expect(true).to.be.ok; // Not recommended
     *
     * Add `.not` earlier in the chain to negate `.ok`.
     *
     *     expect(0).to.equal(0); // Recommended
     *     expect(0).to.not.be.ok; // Not recommended
     *
     *     expect(false).to.be.false; // Recommended
     *     expect(false).to.not.be.ok; // Not recommended
     *
     *     expect(null).to.be.null; // Recommended
     *     expect(null).to.not.be.ok; // Not recommended
     *
     *     expect(undefined).to.be.undefined; // Recommended
     *     expect(undefined).to.not.be.ok; // Not recommended
     *
     * A custom error message can be given as the second argument to `expect`.
     *
     *     expect(false, 'nooo why fail??').to.be.ok;
     *
     * @name ok
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('ok', function () {
      this.assert(
          flag(this, 'object')
        , 'expected #{this} to be truthy'
        , 'expected #{this} to be falsy');
    });

    /**
     * ### .true
     *
     * Asserts that the target is strictly (`===`) equal to `true`.
     *
     *     expect(true).to.be.true;
     *
     * Add `.not` earlier in the chain to negate `.true`. However, it's often best
     * to assert that the target is equal to its expected value, rather than not
     * equal to `true`.
     *
     *     expect(false).to.be.false; // Recommended
     *     expect(false).to.not.be.true; // Not recommended
     *
     *     expect(1).to.equal(1); // Recommended
     *     expect(1).to.not.be.true; // Not recommended
     *
     * A custom error message can be given as the second argument to `expect`.
     *
     *     expect(false, 'nooo why fail??').to.be.true;
     *
     * @name true
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('true', function () {
      this.assert(
          true === flag(this, 'object')
        , 'expected #{this} to be true'
        , 'expected #{this} to be false'
        , flag(this, 'negate') ? false : true
      );
    });

    /**
     * ### .false
     *
     * Asserts that the target is strictly (`===`) equal to `false`.
     *
     *     expect(false).to.be.false;
     *
     * Add `.not` earlier in the chain to negate `.false`. However, it's often
     * best to assert that the target is equal to its expected value, rather than
     * not equal to `false`.
     *
     *     expect(true).to.be.true; // Recommended
     *     expect(true).to.not.be.false; // Not recommended
     *
     *     expect(1).to.equal(1); // Recommended
     *     expect(1).to.not.be.false; // Not recommended
     *
     * A custom error message can be given as the second argument to `expect`.
     *
     *     expect(true, 'nooo why fail??').to.be.false;
     *
     * @name false
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('false', function () {
      this.assert(
          false === flag(this, 'object')
        , 'expected #{this} to be false'
        , 'expected #{this} to be true'
        , flag(this, 'negate') ? true : false
      );
    });

    /**
     * ### .null
     *
     * Asserts that the target is strictly (`===`) equal to `null`.
     *
     *     expect(null).to.be.null;
     *
     * Add `.not` earlier in the chain to negate `.null`. However, it's often best
     * to assert that the target is equal to its expected value, rather than not
     * equal to `null`.
     *
     *     expect(1).to.equal(1); // Recommended
     *     expect(1).to.not.be.null; // Not recommended
     *
     * A custom error message can be given as the second argument to `expect`.
     *
     *     expect(42, 'nooo why fail??').to.be.null;
     *
     * @name null
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('null', function () {
      this.assert(
          null === flag(this, 'object')
        , 'expected #{this} to be null'
        , 'expected #{this} not to be null'
      );
    });

    /**
     * ### .undefined
     *
     * Asserts that the target is strictly (`===`) equal to `undefined`.
     *
     *     expect(undefined).to.be.undefined;
     *
     * Add `.not` earlier in the chain to negate `.undefined`. However, it's often
     * best to assert that the target is equal to its expected value, rather than
     * not equal to `undefined`.
     *
     *     expect(1).to.equal(1); // Recommended
     *     expect(1).to.not.be.undefined; // Not recommended
     *
     * A custom error message can be given as the second argument to `expect`.
     *
     *     expect(42, 'nooo why fail??').to.be.undefined;
     *
     * @name undefined
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('undefined', function () {
      this.assert(
          undefined === flag(this, 'object')
        , 'expected #{this} to be undefined'
        , 'expected #{this} not to be undefined'
      );
    });

    /**
     * ### .NaN
     *
     * Asserts that the target is exactly `NaN`.
     *
     *     expect(NaN).to.be.NaN;
     *
     * Add `.not` earlier in the chain to negate `.NaN`. However, it's often best
     * to assert that the target is equal to its expected value, rather than not
     * equal to `NaN`.
     *
     *     expect('foo').to.equal('foo'); // Recommended
     *     expect('foo').to.not.be.NaN; // Not recommended
     *
     * A custom error message can be given as the second argument to `expect`.
     *
     *     expect(42, 'nooo why fail??').to.be.NaN;
     *
     * @name NaN
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('NaN', function () {
      this.assert(
          _.isNaN(flag(this, 'object'))
          , 'expected #{this} to be NaN'
          , 'expected #{this} not to be NaN'
      );
    });

    /**
     * ### .exist
     *
     * Asserts that the target is not strictly (`===`) equal to either `null` or
     * `undefined`. However, it's often best to assert that the target is equal to
     * its expected value.
     *
     *     expect(1).to.equal(1); // Recommended
     *     expect(1).to.exist; // Not recommended
     *
     *     expect(0).to.equal(0); // Recommended
     *     expect(0).to.exist; // Not recommended
     *
     * Add `.not` earlier in the chain to negate `.exist`.
     *
     *     expect(null).to.be.null; // Recommended
     *     expect(null).to.not.exist; // Not recommended
     *
     *     expect(undefined).to.be.undefined; // Recommended
     *     expect(undefined).to.not.exist; // Not recommended
     *
     * A custom error message can be given as the second argument to `expect`.
     *
     *     expect(null, 'nooo why fail??').to.exist;
     *
     * @name exist
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('exist', function () {
      var val = flag(this, 'object');
      this.assert(
          val !== null && val !== undefined
        , 'expected #{this} to exist'
        , 'expected #{this} to not exist'
      );
    });

    /**
     * ### .empty
     *
     * When the target is a string or array, `.empty` asserts that the target's
     * `length` property is strictly (`===`) equal to `0`.
     *
     *     expect([]).to.be.empty;
     *     expect('').to.be.empty;
     *
     * When the target is a map or set, `.empty` asserts that the target's `size`
     * property is strictly equal to `0`.
     *
     *     expect(new Set()).to.be.empty;
     *     expect(new Map()).to.be.empty;
     *
     * When the target is a non-function object, `.empty` asserts that the target
     * doesn't have any own enumerable properties. Properties with Symbol-based
     * keys are excluded from the count.
     *
     *     expect({}).to.be.empty;
     *
     * Because `.empty` does different things based on the target's type, it's
     * important to check the target's type before using `.empty`. See the `.a`
     * doc for info on testing a target's type.
     *
     *     expect([]).to.be.an('array').that.is.empty;
     *
     * Add `.not` earlier in the chain to negate `.empty`. However, it's often
     * best to assert that the target contains its expected number of values,
     * rather than asserting that it's not empty.
     *
     *     expect([1, 2, 3]).to.have.lengthOf(3); // Recommended
     *     expect([1, 2, 3]).to.not.be.empty; // Not recommended
     *
     *     expect(new Set([1, 2, 3])).to.have.property('size', 3); // Recommended
     *     expect(new Set([1, 2, 3])).to.not.be.empty; // Not recommended
     *
     *     expect(Object.keys({a: 1})).to.have.lengthOf(1); // Recommended
     *     expect({a: 1}).to.not.be.empty; // Not recommended
     *
     * A custom error message can be given as the second argument to `expect`.
     *
     *     expect([1, 2, 3], 'nooo why fail??').to.be.empty;
     *
     * @name empty
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('empty', function () {
      var val = flag(this, 'object')
        , ssfi = flag(this, 'ssfi')
        , flagMsg = flag(this, 'message')
        , itemsCount;

      flagMsg = flagMsg ? flagMsg + ': ' : '';

      switch (_.type(val).toLowerCase()) {
        case 'array':
        case 'string':
          itemsCount = val.length;
          break;
        case 'map':
        case 'set':
          itemsCount = val.size;
          break;
        case 'weakmap':
        case 'weakset':
          throw new AssertionError(
            flagMsg + '.empty was passed a weak collection',
            undefined,
            ssfi
          );
        case 'function':
          var msg = flagMsg + '.empty was passed a function ' + _.getName(val);
          throw new AssertionError(msg.trim(), undefined, ssfi);
        default:
          if (val !== Object(val)) {
            throw new AssertionError(
              flagMsg + '.empty was passed non-string primitive ' + _.inspect(val),
              undefined,
              ssfi
            );
          }
          itemsCount = Object.keys(val).length;
      }

      this.assert(
          0 === itemsCount
        , 'expected #{this} to be empty'
        , 'expected #{this} not to be empty'
      );
    });

    /**
     * ### .arguments
     *
     * Asserts that the target is an `arguments` object.
     *
     *     function test () {
     *       expect(arguments).to.be.arguments;
     *     }
     *
     *     test();
     *
     * Add `.not` earlier in the chain to negate `.arguments`. However, it's often
     * best to assert which type the target is expected to be, rather than
     * asserting that its not an `arguments` object.
     *
     *     expect('foo').to.be.a('string'); // Recommended
     *     expect('foo').to.not.be.arguments; // Not recommended
     *
     * A custom error message can be given as the second argument to `expect`.
     *
     *     expect({}, 'nooo why fail??').to.be.arguments;
     *
     * The alias `.Arguments` can be used interchangeably with `.arguments`.
     *
     * @name arguments
     * @alias Arguments
     * @namespace BDD
     * @api public
     */

    function checkArguments () {
      var obj = flag(this, 'object')
        , type = _.type(obj);
      this.assert(
          'Arguments' === type
        , 'expected #{this} to be arguments but got ' + type
        , 'expected #{this} to not be arguments'
      );
    }

    Assertion.addProperty('arguments', checkArguments);
    Assertion.addProperty('Arguments', checkArguments);

    /**
     * ### .equal(val[, msg])
     *
     * Asserts that the target is strictly (`===`) equal to the given `val`.
     *
     *     expect(1).to.equal(1);
     *     expect('foo').to.equal('foo');
     *
     * Add `.deep` earlier in the chain to use deep equality instead. See the
     * `deep-eql` project page for info on the deep equality algorithm:
     * https://github.com/chaijs/deep-eql.
     *
     *     // Target object deeply (but not strictly) equals `{a: 1}`
     *     expect({a: 1}).to.deep.equal({a: 1});
     *     expect({a: 1}).to.not.equal({a: 1});
     *
     *     // Target array deeply (but not strictly) equals `[1, 2]`
     *     expect([1, 2]).to.deep.equal([1, 2]);
     *     expect([1, 2]).to.not.equal([1, 2]);
     *
     * Add `.not` earlier in the chain to negate `.equal`. However, it's often
     * best to assert that the target is equal to its expected value, rather than
     * not equal to one of countless unexpected values.
     *
     *     expect(1).to.equal(1); // Recommended
     *     expect(1).to.not.equal(2); // Not recommended
     *
     * `.equal` accepts an optional `msg` argument which is a custom error message
     * to show when the assertion fails. The message can also be given as the
     * second argument to `expect`.
     *
     *     expect(1).to.equal(2, 'nooo why fail??');
     *     expect(1, 'nooo why fail??').to.equal(2);
     *
     * The aliases `.equals` and `eq` can be used interchangeably with `.equal`.
     *
     * @name equal
     * @alias equals
     * @alias eq
     * @param {Mixed} val
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    function assertEqual (val, msg) {
      if (msg) flag(this, 'message', msg);
      var obj = flag(this, 'object');
      if (flag(this, 'deep')) {
        return this.eql(val);
      } else {
        this.assert(
            val === obj
          , 'expected #{this} to equal #{exp}'
          , 'expected #{this} to not equal #{exp}'
          , val
          , this._obj
          , true
        );
      }
    }

    Assertion.addMethod('equal', assertEqual);
    Assertion.addMethod('equals', assertEqual);
    Assertion.addMethod('eq', assertEqual);

    /**
     * ### .eql(obj[, msg])
     *
     * Asserts that the target is deeply equal to the given `obj`. See the
     * `deep-eql` project page for info on the deep equality algorithm:
     * https://github.com/chaijs/deep-eql.
     *
     *     // Target object is deeply (but not strictly) equal to {a: 1}
     *     expect({a: 1}).to.eql({a: 1}).but.not.equal({a: 1});
     *
     *     // Target array is deeply (but not strictly) equal to [1, 2]
     *     expect([1, 2]).to.eql([1, 2]).but.not.equal([1, 2]);
     *
     * Add `.not` earlier in the chain to negate `.eql`. However, it's often best
     * to assert that the target is deeply equal to its expected value, rather
     * than not deeply equal to one of countless unexpected values.
     *
     *     expect({a: 1}).to.eql({a: 1}); // Recommended
     *     expect({a: 1}).to.not.eql({b: 2}); // Not recommended
     *
     * `.eql` accepts an optional `msg` argument which is a custom error message
     * to show when the assertion fails. The message can also be given as the
     * second argument to `expect`.
     *
     *     expect({a: 1}).to.eql({b: 2}, 'nooo why fail??');
     *     expect({a: 1}, 'nooo why fail??').to.eql({b: 2});
     *
     * The alias `.eqls` can be used interchangeably with `.eql`.
     *
     * The `.deep.equal` assertion is almost identical to `.eql` but with one
     * difference: `.deep.equal` causes deep equality comparisons to also be used
     * for any other assertions that follow in the chain.
     *
     * @name eql
     * @alias eqls
     * @param {Mixed} obj
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    function assertEql(obj, msg) {
      if (msg) flag(this, 'message', msg);
      this.assert(
          _.eql(obj, flag(this, 'object'))
        , 'expected #{this} to deeply equal #{exp}'
        , 'expected #{this} to not deeply equal #{exp}'
        , obj
        , this._obj
        , true
      );
    }

    Assertion.addMethod('eql', assertEql);
    Assertion.addMethod('eqls', assertEql);

    /**
     * ### .above(n[, msg])
     *
     * Asserts that the target is a number or a date greater than the given number or date `n` respectively.
     * However, it's often best to assert that the target is equal to its expected
     * value.
     *
     *     expect(2).to.equal(2); // Recommended
     *     expect(2).to.be.above(1); // Not recommended
     *
     * Add `.lengthOf` earlier in the chain to assert that the value of the
     * target's `length` property is greater than the given number `n`.
     *
     *     expect('foo').to.have.lengthOf(3); // Recommended
     *     expect('foo').to.have.lengthOf.above(2); // Not recommended
     *
     *     expect([1, 2, 3]).to.have.lengthOf(3); // Recommended
     *     expect([1, 2, 3]).to.have.lengthOf.above(2); // Not recommended
     *
     * Add `.not` earlier in the chain to negate `.above`.
     *
     *     expect(2).to.equal(2); // Recommended
     *     expect(1).to.not.be.above(2); // Not recommended
     *
     * `.above` accepts an optional `msg` argument which is a custom error message
     * to show when the assertion fails. The message can also be given as the
     * second argument to `expect`.
     *
     *     expect(1).to.be.above(2, 'nooo why fail??');
     *     expect(1, 'nooo why fail??').to.be.above(2);
     *
     * The aliases `.gt` and `.greaterThan` can be used interchangeably with
     * `.above`.
     *
     * @name above
     * @alias gt
     * @alias greaterThan
     * @param {Number} n
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    function assertAbove (n, msg) {
      if (msg) flag(this, 'message', msg);
      var obj = flag(this, 'object')
        , doLength = flag(this, 'doLength')
        , flagMsg = flag(this, 'message')
        , msgPrefix = ((flagMsg) ? flagMsg + ': ' : '')
        , ssfi = flag(this, 'ssfi')
        , objType = _.type(obj).toLowerCase()
        , nType = _.type(n).toLowerCase()
        , shouldThrow = true;

      if (doLength) {
        new Assertion(obj, flagMsg, ssfi, true).to.have.property('length');
      }

      if (!doLength && (objType === 'date' && nType !== 'date')) {
        errorMessage = msgPrefix + 'the argument to above must be a date';
      } else if (nType !== 'number' && (doLength || objType === 'number')) {
        errorMessage = msgPrefix + 'the argument to above must be a number';
      } else if (!doLength && (objType !== 'date' && objType !== 'number')) {
        var printObj = (objType === 'string') ? "'" + obj + "'" : obj;
        errorMessage = msgPrefix + 'expected ' + printObj + ' to be a number or a date';
      } else {
        shouldThrow = false;
      }

      if (shouldThrow) {
        throw new AssertionError(errorMessage, undefined, ssfi);
      }

      if (doLength) {
        var len = obj.length;
        this.assert(
            len > n
          , 'expected #{this} to have a length above #{exp} but got #{act}'
          , 'expected #{this} to not have a length above #{exp}'
          , n
          , len
        );
      } else {
        this.assert(
            obj > n
          , 'expected #{this} to be above #{exp}'
          , 'expected #{this} to be at most #{exp}'
          , n
        );
      }
    }

    Assertion.addMethod('above', assertAbove);
    Assertion.addMethod('gt', assertAbove);
    Assertion.addMethod('greaterThan', assertAbove);

    /**
     * ### .least(n[, msg])
     *
     * Asserts that the target is a number or a date greater than or equal to the given
     * number or date `n` respectively. However, it's often best to assert that the target is equal to
     * its expected value.
     *
     *     expect(2).to.equal(2); // Recommended
     *     expect(2).to.be.at.least(1); // Not recommended
     *     expect(2).to.be.at.least(2); // Not recommended
     *
     * Add `.lengthOf` earlier in the chain to assert that the value of the
     * target's `length` property is greater than or equal to the given number
     * `n`.
     *
     *     expect('foo').to.have.lengthOf(3); // Recommended
     *     expect('foo').to.have.lengthOf.at.least(2); // Not recommended
     *
     *     expect([1, 2, 3]).to.have.lengthOf(3); // Recommended
     *     expect([1, 2, 3]).to.have.lengthOf.at.least(2); // Not recommended
     *
     * Add `.not` earlier in the chain to negate `.least`.
     *
     *     expect(1).to.equal(1); // Recommended
     *     expect(1).to.not.be.at.least(2); // Not recommended
     *
     * `.least` accepts an optional `msg` argument which is a custom error message
     * to show when the assertion fails. The message can also be given as the
     * second argument to `expect`.
     *
     *     expect(1).to.be.at.least(2, 'nooo why fail??');
     *     expect(1, 'nooo why fail??').to.be.at.least(2);
     *
     * The alias `.gte` can be used interchangeably with `.least`.
     *
     * @name least
     * @alias gte
     * @param {Number} n
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    function assertLeast (n, msg) {
      if (msg) flag(this, 'message', msg);
      var obj = flag(this, 'object')
        , doLength = flag(this, 'doLength')
        , flagMsg = flag(this, 'message')
        , msgPrefix = ((flagMsg) ? flagMsg + ': ' : '')
        , ssfi = flag(this, 'ssfi')
        , objType = _.type(obj).toLowerCase()
        , nType = _.type(n).toLowerCase()
        , shouldThrow = true;

      if (doLength) {
        new Assertion(obj, flagMsg, ssfi, true).to.have.property('length');
      }

      if (!doLength && (objType === 'date' && nType !== 'date')) {
        errorMessage = msgPrefix + 'the argument to least must be a date';
      } else if (nType !== 'number' && (doLength || objType === 'number')) {
        errorMessage = msgPrefix + 'the argument to least must be a number';
      } else if (!doLength && (objType !== 'date' && objType !== 'number')) {
        var printObj = (objType === 'string') ? "'" + obj + "'" : obj;
        errorMessage = msgPrefix + 'expected ' + printObj + ' to be a number or a date';
      } else {
        shouldThrow = false;
      }

      if (shouldThrow) {
        throw new AssertionError(errorMessage, undefined, ssfi);
      }

      if (doLength) {
        var len = obj.length;
        this.assert(
            len >= n
          , 'expected #{this} to have a length at least #{exp} but got #{act}'
          , 'expected #{this} to have a length below #{exp}'
          , n
          , len
        );
      } else {
        this.assert(
            obj >= n
          , 'expected #{this} to be at least #{exp}'
          , 'expected #{this} to be below #{exp}'
          , n
        );
      }
    }

    Assertion.addMethod('least', assertLeast);
    Assertion.addMethod('gte', assertLeast);

    /**
     * ### .below(n[, msg])
     *
     * Asserts that the target is a number or a date less than the given number or date `n` respectively.
     * However, it's often best to assert that the target is equal to its expected
     * value.
     *
     *     expect(1).to.equal(1); // Recommended
     *     expect(1).to.be.below(2); // Not recommended
     *
     * Add `.lengthOf` earlier in the chain to assert that the value of the
     * target's `length` property is less than the given number `n`.
     *
     *     expect('foo').to.have.lengthOf(3); // Recommended
     *     expect('foo').to.have.lengthOf.below(4); // Not recommended
     *
     *     expect([1, 2, 3]).to.have.length(3); // Recommended
     *     expect([1, 2, 3]).to.have.lengthOf.below(4); // Not recommended
     *
     * Add `.not` earlier in the chain to negate `.below`.
     *
     *     expect(2).to.equal(2); // Recommended
     *     expect(2).to.not.be.below(1); // Not recommended
     *
     * `.below` accepts an optional `msg` argument which is a custom error message
     * to show when the assertion fails. The message can also be given as the
     * second argument to `expect`.
     *
     *     expect(2).to.be.below(1, 'nooo why fail??');
     *     expect(2, 'nooo why fail??').to.be.below(1);
     *
     * The aliases `.lt` and `.lessThan` can be used interchangeably with
     * `.below`.
     *
     * @name below
     * @alias lt
     * @alias lessThan
     * @param {Number} n
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    function assertBelow (n, msg) {
      if (msg) flag(this, 'message', msg);
      var obj = flag(this, 'object')
        , doLength = flag(this, 'doLength')
        , flagMsg = flag(this, 'message')
        , msgPrefix = ((flagMsg) ? flagMsg + ': ' : '')
        , ssfi = flag(this, 'ssfi')
        , objType = _.type(obj).toLowerCase()
        , nType = _.type(n).toLowerCase()
        , shouldThrow = true;

      if (doLength) {
        new Assertion(obj, flagMsg, ssfi, true).to.have.property('length');
      }

      if (!doLength && (objType === 'date' && nType !== 'date')) {
        errorMessage = msgPrefix + 'the argument to below must be a date';
      } else if (nType !== 'number' && (doLength || objType === 'number')) {
        errorMessage = msgPrefix + 'the argument to below must be a number';
      } else if (!doLength && (objType !== 'date' && objType !== 'number')) {
        var printObj = (objType === 'string') ? "'" + obj + "'" : obj;
        errorMessage = msgPrefix + 'expected ' + printObj + ' to be a number or a date';
      } else {
        shouldThrow = false;
      }

      if (shouldThrow) {
        throw new AssertionError(errorMessage, undefined, ssfi);
      }

      if (doLength) {
        var len = obj.length;
        this.assert(
            len < n
          , 'expected #{this} to have a length below #{exp} but got #{act}'
          , 'expected #{this} to not have a length below #{exp}'
          , n
          , len
        );
      } else {
        this.assert(
            obj < n
          , 'expected #{this} to be below #{exp}'
          , 'expected #{this} to be at least #{exp}'
          , n
        );
      }
    }

    Assertion.addMethod('below', assertBelow);
    Assertion.addMethod('lt', assertBelow);
    Assertion.addMethod('lessThan', assertBelow);

    /**
     * ### .most(n[, msg])
     *
     * Asserts that the target is a number or a date less than or equal to the given number
     * or date `n` respectively. However, it's often best to assert that the target is equal to its
     * expected value.
     *
     *     expect(1).to.equal(1); // Recommended
     *     expect(1).to.be.at.most(2); // Not recommended
     *     expect(1).to.be.at.most(1); // Not recommended
     *
     * Add `.lengthOf` earlier in the chain to assert that the value of the
     * target's `length` property is less than or equal to the given number `n`.
     *
     *     expect('foo').to.have.lengthOf(3); // Recommended
     *     expect('foo').to.have.lengthOf.at.most(4); // Not recommended
     *
     *     expect([1, 2, 3]).to.have.lengthOf(3); // Recommended
     *     expect([1, 2, 3]).to.have.lengthOf.at.most(4); // Not recommended
     *
     * Add `.not` earlier in the chain to negate `.most`.
     *
     *     expect(2).to.equal(2); // Recommended
     *     expect(2).to.not.be.at.most(1); // Not recommended
     *
     * `.most` accepts an optional `msg` argument which is a custom error message
     * to show when the assertion fails. The message can also be given as the
     * second argument to `expect`.
     *
     *     expect(2).to.be.at.most(1, 'nooo why fail??');
     *     expect(2, 'nooo why fail??').to.be.at.most(1);
     *
     * The alias `.lte` can be used interchangeably with `.most`.
     *
     * @name most
     * @alias lte
     * @param {Number} n
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    function assertMost (n, msg) {
      if (msg) flag(this, 'message', msg);
      var obj = flag(this, 'object')
        , doLength = flag(this, 'doLength')
        , flagMsg = flag(this, 'message')
        , msgPrefix = ((flagMsg) ? flagMsg + ': ' : '')
        , ssfi = flag(this, 'ssfi')
        , objType = _.type(obj).toLowerCase()
        , nType = _.type(n).toLowerCase()
        , shouldThrow = true;

      if (doLength) {
        new Assertion(obj, flagMsg, ssfi, true).to.have.property('length');
      }

      if (!doLength && (objType === 'date' && nType !== 'date')) {
        errorMessage = msgPrefix + 'the argument to most must be a date';
      } else if (nType !== 'number' && (doLength || objType === 'number')) {
        errorMessage = msgPrefix + 'the argument to most must be a number';
      } else if (!doLength && (objType !== 'date' && objType !== 'number')) {
        var printObj = (objType === 'string') ? "'" + obj + "'" : obj;
        errorMessage = msgPrefix + 'expected ' + printObj + ' to be a number or a date';
      } else {
        shouldThrow = false;
      }

      if (shouldThrow) {
        throw new AssertionError(errorMessage, undefined, ssfi);
      }

      if (doLength) {
        var len = obj.length;
        this.assert(
            len <= n
          , 'expected #{this} to have a length at most #{exp} but got #{act}'
          , 'expected #{this} to have a length above #{exp}'
          , n
          , len
        );
      } else {
        this.assert(
            obj <= n
          , 'expected #{this} to be at most #{exp}'
          , 'expected #{this} to be above #{exp}'
          , n
        );
      }
    }

    Assertion.addMethod('most', assertMost);
    Assertion.addMethod('lte', assertMost);

    /**
     * ### .within(start, finish[, msg])
     *
     * Asserts that the target is a number or a date greater than or equal to the given
     * number or date `start`, and less than or equal to the given number or date `finish` respectively.
     * However, it's often best to assert that the target is equal to its expected
     * value.
     *
     *     expect(2).to.equal(2); // Recommended
     *     expect(2).to.be.within(1, 3); // Not recommended
     *     expect(2).to.be.within(2, 3); // Not recommended
     *     expect(2).to.be.within(1, 2); // Not recommended
     *
     * Add `.lengthOf` earlier in the chain to assert that the value of the
     * target's `length` property is greater than or equal to the given number
     * `start`, and less than or equal to the given number `finish`.
     *
     *     expect('foo').to.have.lengthOf(3); // Recommended
     *     expect('foo').to.have.lengthOf.within(2, 4); // Not recommended
     *
     *     expect([1, 2, 3]).to.have.lengthOf(3); // Recommended
     *     expect([1, 2, 3]).to.have.lengthOf.within(2, 4); // Not recommended
     *
     * Add `.not` earlier in the chain to negate `.within`.
     *
     *     expect(1).to.equal(1); // Recommended
     *     expect(1).to.not.be.within(2, 4); // Not recommended
     *
     * `.within` accepts an optional `msg` argument which is a custom error
     * message to show when the assertion fails. The message can also be given as
     * the second argument to `expect`.
     *
     *     expect(4).to.be.within(1, 3, 'nooo why fail??');
     *     expect(4, 'nooo why fail??').to.be.within(1, 3);
     *
     * @name within
     * @param {Number} start lower bound inclusive
     * @param {Number} finish upper bound inclusive
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    Assertion.addMethod('within', function (start, finish, msg) {
      if (msg) flag(this, 'message', msg);
      var obj = flag(this, 'object')
        , doLength = flag(this, 'doLength')
        , flagMsg = flag(this, 'message')
        , msgPrefix = ((flagMsg) ? flagMsg + ': ' : '')
        , ssfi = flag(this, 'ssfi')
        , objType = _.type(obj).toLowerCase()
        , startType = _.type(start).toLowerCase()
        , finishType = _.type(finish).toLowerCase()
        , shouldThrow = true
        , range = (startType === 'date' && finishType === 'date')
            ? start.toUTCString() + '..' + finish.toUTCString()
            : start + '..' + finish;

      if (doLength) {
        new Assertion(obj, flagMsg, ssfi, true).to.have.property('length');
      }

      if (!doLength && (objType === 'date' && (startType !== 'date' || finishType !== 'date'))) {
        errorMessage = msgPrefix + 'the arguments to within must be dates';
      } else if ((startType !== 'number' || finishType !== 'number') && (doLength || objType === 'number')) {
        errorMessage = msgPrefix + 'the arguments to within must be numbers';
      } else if (!doLength && (objType !== 'date' && objType !== 'number')) {
        var printObj = (objType === 'string') ? "'" + obj + "'" : obj;
        errorMessage = msgPrefix + 'expected ' + printObj + ' to be a number or a date';
      } else {
        shouldThrow = false;
      }

      if (shouldThrow) {
        throw new AssertionError(errorMessage, undefined, ssfi);
      }

      if (doLength) {
        var len = obj.length;
        this.assert(
            len >= start && len <= finish
          , 'expected #{this} to have a length within ' + range
          , 'expected #{this} to not have a length within ' + range
        );
      } else {
        this.assert(
            obj >= start && obj <= finish
          , 'expected #{this} to be within ' + range
          , 'expected #{this} to not be within ' + range
        );
      }
    });

    /**
     * ### .instanceof(constructor[, msg])
     *
     * Asserts that the target is an instance of the given `constructor`.
     *
     *     function Cat () { }
     *
     *     expect(new Cat()).to.be.an.instanceof(Cat);
     *     expect([1, 2]).to.be.an.instanceof(Array);
     *
     * Add `.not` earlier in the chain to negate `.instanceof`.
     *
     *     expect({a: 1}).to.not.be.an.instanceof(Array);
     *
     * `.instanceof` accepts an optional `msg` argument which is a custom error
     * message to show when the assertion fails. The message can also be given as
     * the second argument to `expect`.
     *
     *     expect(1).to.be.an.instanceof(Array, 'nooo why fail??');
     *     expect(1, 'nooo why fail??').to.be.an.instanceof(Array);
     *
     * Due to limitations in ES5, `.instanceof` may not always work as expected
     * when using a transpiler such as Babel or TypeScript. In particular, it may
     * produce unexpected results when subclassing built-in object such as
     * `Array`, `Error`, and `Map`. See your transpiler's docs for details:
     *
     * - ([Babel](https://babeljs.io/docs/usage/caveats/#classes))
     * - ([TypeScript](https://github.com/Microsoft/TypeScript/wiki/Breaking-Changes#extending-built-ins-like-error-array-and-map-may-no-longer-work))
     *
     * The alias `.instanceOf` can be used interchangeably with `.instanceof`.
     *
     * @name instanceof
     * @param {Constructor} constructor
     * @param {String} msg _optional_
     * @alias instanceOf
     * @namespace BDD
     * @api public
     */

    function assertInstanceOf (constructor, msg) {
      if (msg) flag(this, 'message', msg);

      var target = flag(this, 'object')
      var ssfi = flag(this, 'ssfi');
      var flagMsg = flag(this, 'message');

      try {
        var isInstanceOf = target instanceof constructor;
      } catch (err) {
        if (err instanceof TypeError) {
          flagMsg = flagMsg ? flagMsg + ': ' : '';
          throw new AssertionError(
            flagMsg + 'The instanceof assertion needs a constructor but '
              + _.type(constructor) + ' was given.',
            undefined,
            ssfi
          );
        }
        throw err;
      }

      var name = _.getName(constructor);
      if (name === null) {
        name = 'an unnamed constructor';
      }

      this.assert(
          isInstanceOf
        , 'expected #{this} to be an instance of ' + name
        , 'expected #{this} to not be an instance of ' + name
      );
    };

    Assertion.addMethod('instanceof', assertInstanceOf);
    Assertion.addMethod('instanceOf', assertInstanceOf);

    /**
     * ### .property(name[, val[, msg]])
     *
     * Asserts that the target has a property with the given key `name`.
     *
     *     expect({a: 1}).to.have.property('a');
     *
     * When `val` is provided, `.property` also asserts that the property's value
     * is equal to the given `val`.
     *
     *     expect({a: 1}).to.have.property('a', 1);
     *
     * By default, strict (`===`) equality is used. Add `.deep` earlier in the
     * chain to use deep equality instead. See the `deep-eql` project page for
     * info on the deep equality algorithm: https://github.com/chaijs/deep-eql.
     *
     *     // Target object deeply (but not strictly) has property `x: {a: 1}`
     *     expect({x: {a: 1}}).to.have.deep.property('x', {a: 1});
     *     expect({x: {a: 1}}).to.not.have.property('x', {a: 1});
     *
     * The target's enumerable and non-enumerable properties are always included
     * in the search. By default, both own and inherited properties are included.
     * Add `.own` earlier in the chain to exclude inherited properties from the
     * search.
     *
     *     Object.prototype.b = 2;
     *
     *     expect({a: 1}).to.have.own.property('a');
     *     expect({a: 1}).to.have.own.property('a', 1);
     *     expect({a: 1}).to.have.property('b').but.not.own.property('b');
     *
     * `.deep` and `.own` can be combined.
     *
     *     expect({x: {a: 1}}).to.have.deep.own.property('x', {a: 1});
     *
     * Add `.nested` earlier in the chain to enable dot- and bracket-notation when
     * referencing nested properties.
     *
     *     expect({a: {b: ['x', 'y']}}).to.have.nested.property('a.b[1]');
     *     expect({a: {b: ['x', 'y']}}).to.have.nested.property('a.b[1]', 'y');
     *
     * If `.` or `[]` are part of an actual property name, they can be escaped by
     * adding two backslashes before them.
     *
     *     expect({'.a': {'[b]': 'x'}}).to.have.nested.property('\\.a.\\[b\\]');
     *
     * `.deep` and `.nested` can be combined.
     *
     *     expect({a: {b: [{c: 3}]}})
     *       .to.have.deep.nested.property('a.b[0]', {c: 3});
     *
     * `.own` and `.nested` cannot be combined.
     *
     * Add `.not` earlier in the chain to negate `.property`.
     *
     *     expect({a: 1}).to.not.have.property('b');
     *
     * However, it's dangerous to negate `.property` when providing `val`. The
     * problem is that it creates uncertain expectations by asserting that the
     * target either doesn't have a property with the given key `name`, or that it
     * does have a property with the given key `name` but its value isn't equal to
     * the given `val`. It's often best to identify the exact output that's
     * expected, and then write an assertion that only accepts that exact output.
     *
     * When the target isn't expected to have a property with the given key
     * `name`, it's often best to assert exactly that.
     *
     *     expect({b: 2}).to.not.have.property('a'); // Recommended
     *     expect({b: 2}).to.not.have.property('a', 1); // Not recommended
     *
     * When the target is expected to have a property with the given key `name`,
     * it's often best to assert that the property has its expected value, rather
     * than asserting that it doesn't have one of many unexpected values.
     *
     *     expect({a: 3}).to.have.property('a', 3); // Recommended
     *     expect({a: 3}).to.not.have.property('a', 1); // Not recommended
     *
     * `.property` changes the target of any assertions that follow in the chain
     * to be the value of the property from the original target object.
     *
     *     expect({a: 1}).to.have.property('a').that.is.a('number');
     *
     * `.property` accepts an optional `msg` argument which is a custom error
     * message to show when the assertion fails. The message can also be given as
     * the second argument to `expect`. When not providing `val`, only use the
     * second form.
     *
     *     // Recommended
     *     expect({a: 1}).to.have.property('a', 2, 'nooo why fail??');
     *     expect({a: 1}, 'nooo why fail??').to.have.property('a', 2);
     *     expect({a: 1}, 'nooo why fail??').to.have.property('b');
     *
     *     // Not recommended
     *     expect({a: 1}).to.have.property('b', undefined, 'nooo why fail??');
     *
     * The above assertion isn't the same thing as not providing `val`. Instead,
     * it's asserting that the target object has a `b` property that's equal to
     * `undefined`.
     *
     * The assertions `.ownProperty` and `.haveOwnProperty` can be used
     * interchangeably with `.own.property`.
     *
     * @name property
     * @param {String} name
     * @param {Mixed} val (optional)
     * @param {String} msg _optional_
     * @returns value of property for chaining
     * @namespace BDD
     * @api public
     */

    function assertProperty (name, val, msg) {
      if (msg) flag(this, 'message', msg);

      var isNested = flag(this, 'nested')
        , isOwn = flag(this, 'own')
        , flagMsg = flag(this, 'message')
        , obj = flag(this, 'object')
        , ssfi = flag(this, 'ssfi');

      if (isNested && isOwn) {
        flagMsg = flagMsg ? flagMsg + ': ' : '';
        throw new AssertionError(
          flagMsg + 'The "nested" and "own" flags cannot be combined.',
          undefined,
          ssfi
        );
      }

      if (obj === null || obj === undefined) {
        flagMsg = flagMsg ? flagMsg + ': ' : '';
        throw new AssertionError(
          flagMsg + 'Target cannot be null or undefined.',
          undefined,
          ssfi
        );
      }

      var isDeep = flag(this, 'deep')
        , negate = flag(this, 'negate')
        , pathInfo = isNested ? _.getPathInfo(obj, name) : null
        , value = isNested ? pathInfo.value : obj[name];

      var descriptor = '';
      if (isDeep) descriptor += 'deep ';
      if (isOwn) descriptor += 'own ';
      if (isNested) descriptor += 'nested ';
      descriptor += 'property ';

      var hasProperty;
      if (isOwn) hasProperty = Object.prototype.hasOwnProperty.call(obj, name);
      else if (isNested) hasProperty = pathInfo.exists;
      else hasProperty = _.hasProperty(obj, name);

      // When performing a negated assertion for both name and val, merely having
      // a property with the given name isn't enough to cause the assertion to
      // fail. It must both have a property with the given name, and the value of
      // that property must equal the given val. Therefore, skip this assertion in
      // favor of the next.
      if (!negate || arguments.length === 1) {
        this.assert(
            hasProperty
          , 'expected #{this} to have ' + descriptor + _.inspect(name)
          , 'expected #{this} to not have ' + descriptor + _.inspect(name));
      }

      if (arguments.length > 1) {
        this.assert(
            hasProperty && (isDeep ? _.eql(val, value) : val === value)
          , 'expected #{this} to have ' + descriptor + _.inspect(name) + ' of #{exp}, but got #{act}'
          , 'expected #{this} to not have ' + descriptor + _.inspect(name) + ' of #{act}'
          , val
          , value
        );
      }

      flag(this, 'object', value);
    }

    Assertion.addMethod('property', assertProperty);

    function assertOwnProperty (name, value, msg) {
      flag(this, 'own', true);
      assertProperty.apply(this, arguments);
    }

    Assertion.addMethod('ownProperty', assertOwnProperty);
    Assertion.addMethod('haveOwnProperty', assertOwnProperty);

    /**
     * ### .ownPropertyDescriptor(name[, descriptor[, msg]])
     *
     * Asserts that the target has its own property descriptor with the given key
     * `name`. Enumerable and non-enumerable properties are included in the
     * search.
     *
     *     expect({a: 1}).to.have.ownPropertyDescriptor('a');
     *
     * When `descriptor` is provided, `.ownPropertyDescriptor` also asserts that
     * the property's descriptor is deeply equal to the given `descriptor`. See
     * the `deep-eql` project page for info on the deep equality algorithm:
     * https://github.com/chaijs/deep-eql.
     *
     *     expect({a: 1}).to.have.ownPropertyDescriptor('a', {
     *       configurable: true,
     *       enumerable: true,
     *       writable: true,
     *       value: 1,
     *     });
     *
     * Add `.not` earlier in the chain to negate `.ownPropertyDescriptor`.
     *
     *     expect({a: 1}).to.not.have.ownPropertyDescriptor('b');
     *
     * However, it's dangerous to negate `.ownPropertyDescriptor` when providing
     * a `descriptor`. The problem is that it creates uncertain expectations by
     * asserting that the target either doesn't have a property descriptor with
     * the given key `name`, or that it does have a property descriptor with the
     * given key `name` but its not deeply equal to the given `descriptor`. It's
     * often best to identify the exact output that's expected, and then write an
     * assertion that only accepts that exact output.
     *
     * When the target isn't expected to have a property descriptor with the given
     * key `name`, it's often best to assert exactly that.
     *
     *     // Recommended
     *     expect({b: 2}).to.not.have.ownPropertyDescriptor('a');
     *
     *     // Not recommended
     *     expect({b: 2}).to.not.have.ownPropertyDescriptor('a', {
     *       configurable: true,
     *       enumerable: true,
     *       writable: true,
     *       value: 1,
     *     });
     *
     * When the target is expected to have a property descriptor with the given
     * key `name`, it's often best to assert that the property has its expected
     * descriptor, rather than asserting that it doesn't have one of many
     * unexpected descriptors.
     *
     *     // Recommended
     *     expect({a: 3}).to.have.ownPropertyDescriptor('a', {
     *       configurable: true,
     *       enumerable: true,
     *       writable: true,
     *       value: 3,
     *     });
     *
     *     // Not recommended
     *     expect({a: 3}).to.not.have.ownPropertyDescriptor('a', {
     *       configurable: true,
     *       enumerable: true,
     *       writable: true,
     *       value: 1,
     *     });
     *
     * `.ownPropertyDescriptor` changes the target of any assertions that follow
     * in the chain to be the value of the property descriptor from the original
     * target object.
     *
     *     expect({a: 1}).to.have.ownPropertyDescriptor('a')
     *       .that.has.property('enumerable', true);
     *
     * `.ownPropertyDescriptor` accepts an optional `msg` argument which is a
     * custom error message to show when the assertion fails. The message can also
     * be given as the second argument to `expect`. When not providing
     * `descriptor`, only use the second form.
     *
     *     // Recommended
     *     expect({a: 1}).to.have.ownPropertyDescriptor('a', {
     *       configurable: true,
     *       enumerable: true,
     *       writable: true,
     *       value: 2,
     *     }, 'nooo why fail??');
     *
     *     // Recommended
     *     expect({a: 1}, 'nooo why fail??').to.have.ownPropertyDescriptor('a', {
     *       configurable: true,
     *       enumerable: true,
     *       writable: true,
     *       value: 2,
     *     });
     *
     *     // Recommended
     *     expect({a: 1}, 'nooo why fail??').to.have.ownPropertyDescriptor('b');
     *
     *     // Not recommended
     *     expect({a: 1})
     *       .to.have.ownPropertyDescriptor('b', undefined, 'nooo why fail??');
     *
     * The above assertion isn't the same thing as not providing `descriptor`.
     * Instead, it's asserting that the target object has a `b` property
     * descriptor that's deeply equal to `undefined`.
     *
     * The alias `.haveOwnPropertyDescriptor` can be used interchangeably with
     * `.ownPropertyDescriptor`.
     *
     * @name ownPropertyDescriptor
     * @alias haveOwnPropertyDescriptor
     * @param {String} name
     * @param {Object} descriptor _optional_
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    function assertOwnPropertyDescriptor (name, descriptor, msg) {
      if (typeof descriptor === 'string') {
        msg = descriptor;
        descriptor = null;
      }
      if (msg) flag(this, 'message', msg);
      var obj = flag(this, 'object');
      var actualDescriptor = Object.getOwnPropertyDescriptor(Object(obj), name);
      if (actualDescriptor && descriptor) {
        this.assert(
            _.eql(descriptor, actualDescriptor)
          , 'expected the own property descriptor for ' + _.inspect(name) + ' on #{this} to match ' + _.inspect(descriptor) + ', got ' + _.inspect(actualDescriptor)
          , 'expected the own property descriptor for ' + _.inspect(name) + ' on #{this} to not match ' + _.inspect(descriptor)
          , descriptor
          , actualDescriptor
          , true
        );
      } else {
        this.assert(
            actualDescriptor
          , 'expected #{this} to have an own property descriptor for ' + _.inspect(name)
          , 'expected #{this} to not have an own property descriptor for ' + _.inspect(name)
        );
      }
      flag(this, 'object', actualDescriptor);
    }

    Assertion.addMethod('ownPropertyDescriptor', assertOwnPropertyDescriptor);
    Assertion.addMethod('haveOwnPropertyDescriptor', assertOwnPropertyDescriptor);

    /**
     * ### .lengthOf(n[, msg])
     *
     * Asserts that the target's `length` property is equal to the given number
     * `n`.
     *
     *     expect([1, 2, 3]).to.have.lengthOf(3);
     *     expect('foo').to.have.lengthOf(3);
     *
     * Add `.not` earlier in the chain to negate `.lengthOf`. However, it's often
     * best to assert that the target's `length` property is equal to its expected
     * value, rather than not equal to one of many unexpected values.
     *
     *     expect('foo').to.have.lengthOf(3); // Recommended
     *     expect('foo').to.not.have.lengthOf(4); // Not recommended
     *
     * `.lengthOf` accepts an optional `msg` argument which is a custom error
     * message to show when the assertion fails. The message can also be given as
     * the second argument to `expect`.
     *
     *     expect([1, 2, 3]).to.have.lengthOf(2, 'nooo why fail??');
     *     expect([1, 2, 3], 'nooo why fail??').to.have.lengthOf(2);
     *
     * `.lengthOf` can also be used as a language chain, causing all `.above`,
     * `.below`, `.least`, `.most`, and `.within` assertions that follow in the
     * chain to use the target's `length` property as the target. However, it's
     * often best to assert that the target's `length` property is equal to its
     * expected length, rather than asserting that its `length` property falls
     * within some range of values.
     *
     *     // Recommended
     *     expect([1, 2, 3]).to.have.lengthOf(3);
     *
     *     // Not recommended
     *     expect([1, 2, 3]).to.have.lengthOf.above(2);
     *     expect([1, 2, 3]).to.have.lengthOf.below(4);
     *     expect([1, 2, 3]).to.have.lengthOf.at.least(3);
     *     expect([1, 2, 3]).to.have.lengthOf.at.most(3);
     *     expect([1, 2, 3]).to.have.lengthOf.within(2,4);
     *
     * Due to a compatibility issue, the alias `.length` can't be chained directly
     * off of an uninvoked method such as `.a`. Therefore, `.length` can't be used
     * interchangeably with `.lengthOf` in every situation. It's recommended to
     * always use `.lengthOf` instead of `.length`.
     *
     *     expect([1, 2, 3]).to.have.a.length(3); // incompatible; throws error
     *     expect([1, 2, 3]).to.have.a.lengthOf(3);  // passes as expected
     *
     * @name lengthOf
     * @alias length
     * @param {Number} n
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    function assertLengthChain () {
      flag(this, 'doLength', true);
    }

    function assertLength (n, msg) {
      if (msg) flag(this, 'message', msg);
      var obj = flag(this, 'object')
        , flagMsg = flag(this, 'message')
        , ssfi = flag(this, 'ssfi');
      new Assertion(obj, flagMsg, ssfi, true).to.have.property('length');
      var len = obj.length;

      this.assert(
          len == n
        , 'expected #{this} to have a length of #{exp} but got #{act}'
        , 'expected #{this} to not have a length of #{act}'
        , n
        , len
      );
    }

    Assertion.addChainableMethod('length', assertLength, assertLengthChain);
    Assertion.addChainableMethod('lengthOf', assertLength, assertLengthChain);

    /**
     * ### .match(re[, msg])
     *
     * Asserts that the target matches the given regular expression `re`.
     *
     *     expect('foobar').to.match(/^foo/);
     *
     * Add `.not` earlier in the chain to negate `.match`.
     *
     *     expect('foobar').to.not.match(/taco/);
     *
     * `.match` accepts an optional `msg` argument which is a custom error message
     * to show when the assertion fails. The message can also be given as the
     * second argument to `expect`.
     *
     *     expect('foobar').to.match(/taco/, 'nooo why fail??');
     *     expect('foobar', 'nooo why fail??').to.match(/taco/);
     *
     * The alias `.matches` can be used interchangeably with `.match`.
     *
     * @name match
     * @alias matches
     * @param {RegExp} re
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */
    function assertMatch(re, msg) {
      if (msg) flag(this, 'message', msg);
      var obj = flag(this, 'object');
      this.assert(
          re.exec(obj)
        , 'expected #{this} to match ' + re
        , 'expected #{this} not to match ' + re
      );
    }

    Assertion.addMethod('match', assertMatch);
    Assertion.addMethod('matches', assertMatch);

    /**
     * ### .string(str[, msg])
     *
     * Asserts that the target string contains the given substring `str`.
     *
     *     expect('foobar').to.have.string('bar');
     *
     * Add `.not` earlier in the chain to negate `.string`.
     *
     *     expect('foobar').to.not.have.string('taco');
     *
     * `.string` accepts an optional `msg` argument which is a custom error
     * message to show when the assertion fails. The message can also be given as
     * the second argument to `expect`.
     *
     *     expect('foobar').to.have.string(/taco/, 'nooo why fail??');
     *     expect('foobar', 'nooo why fail??').to.have.string(/taco/);
     *
     * @name string
     * @param {String} str
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    Assertion.addMethod('string', function (str, msg) {
      if (msg) flag(this, 'message', msg);
      var obj = flag(this, 'object')
        , flagMsg = flag(this, 'message')
        , ssfi = flag(this, 'ssfi');
      new Assertion(obj, flagMsg, ssfi, true).is.a('string');

      this.assert(
          ~obj.indexOf(str)
        , 'expected #{this} to contain ' + _.inspect(str)
        , 'expected #{this} to not contain ' + _.inspect(str)
      );
    });

    /**
     * ### .keys(key1[, key2[, ...]])
     *
     * Asserts that the target object, array, map, or set has the given keys. Only
     * the target's own inherited properties are included in the search.
     *
     * When the target is an object or array, keys can be provided as one or more
     * string arguments, a single array argument, or a single object argument. In
     * the latter case, only the keys in the given object matter; the values are
     * ignored.
     *
     *     expect({a: 1, b: 2}).to.have.all.keys('a', 'b');
     *     expect(['x', 'y']).to.have.all.keys(0, 1);
     *
     *     expect({a: 1, b: 2}).to.have.all.keys(['a', 'b']);
     *     expect(['x', 'y']).to.have.all.keys([0, 1]);
     *
     *     expect({a: 1, b: 2}).to.have.all.keys({a: 4, b: 5}); // ignore 4 and 5
     *     expect(['x', 'y']).to.have.all.keys({0: 4, 1: 5}); // ignore 4 and 5
     *
     * When the target is a map or set, each key must be provided as a separate
     * argument.
     *
     *     expect(new Map([['a', 1], ['b', 2]])).to.have.all.keys('a', 'b');
     *     expect(new Set(['a', 'b'])).to.have.all.keys('a', 'b');
     *
     * Because `.keys` does different things based on the target's type, it's
     * important to check the target's type before using `.keys`. See the `.a` doc
     * for info on testing a target's type.
     *
     *     expect({a: 1, b: 2}).to.be.an('object').that.has.all.keys('a', 'b');
     *
     * By default, strict (`===`) equality is used to compare keys of maps and
     * sets. Add `.deep` earlier in the chain to use deep equality instead. See
     * the `deep-eql` project page for info on the deep equality algorithm:
     * https://github.com/chaijs/deep-eql.
     *
     *     // Target set deeply (but not strictly) has key `{a: 1}`
     *     expect(new Set([{a: 1}])).to.have.all.deep.keys([{a: 1}]);
     *     expect(new Set([{a: 1}])).to.not.have.all.keys([{a: 1}]);
     *
     * By default, the target must have all of the given keys and no more. Add
     * `.any` earlier in the chain to only require that the target have at least
     * one of the given keys. Also, add `.not` earlier in the chain to negate
     * `.keys`. It's often best to add `.any` when negating `.keys`, and to use
     * `.all` when asserting `.keys` without negation.
     *
     * When negating `.keys`, `.any` is preferred because `.not.any.keys` asserts
     * exactly what's expected of the output, whereas `.not.all.keys` creates
     * uncertain expectations.
     *
     *     // Recommended; asserts that target doesn't have any of the given keys
     *     expect({a: 1, b: 2}).to.not.have.any.keys('c', 'd');
     *
     *     // Not recommended; asserts that target doesn't have all of the given
     *     // keys but may or may not have some of them
     *     expect({a: 1, b: 2}).to.not.have.all.keys('c', 'd');
     *
     * When asserting `.keys` without negation, `.all` is preferred because
     * `.all.keys` asserts exactly what's expected of the output, whereas
     * `.any.keys` creates uncertain expectations.
     *
     *     // Recommended; asserts that target has all the given keys
     *     expect({a: 1, b: 2}).to.have.all.keys('a', 'b');
     *
     *     // Not recommended; asserts that target has at least one of the given
     *     // keys but may or may not have more of them
     *     expect({a: 1, b: 2}).to.have.any.keys('a', 'b');
     *
     * Note that `.all` is used by default when neither `.all` nor `.any` appear
     * earlier in the chain. However, it's often best to add `.all` anyway because
     * it improves readability.
     *
     *     // Both assertions are identical
     *     expect({a: 1, b: 2}).to.have.all.keys('a', 'b'); // Recommended
     *     expect({a: 1, b: 2}).to.have.keys('a', 'b'); // Not recommended
     *
     * Add `.include` earlier in the chain to require that the target's keys be a
     * superset of the expected keys, rather than identical sets.
     *
     *     // Target object's keys are a superset of ['a', 'b'] but not identical
     *     expect({a: 1, b: 2, c: 3}).to.include.all.keys('a', 'b');
     *     expect({a: 1, b: 2, c: 3}).to.not.have.all.keys('a', 'b');
     *
     * However, if `.any` and `.include` are combined, only the `.any` takes
     * effect. The `.include` is ignored in this case.
     *
     *     // Both assertions are identical
     *     expect({a: 1}).to.have.any.keys('a', 'b');
     *     expect({a: 1}).to.include.any.keys('a', 'b');
     *
     * A custom error message can be given as the second argument to `expect`.
     *
     *     expect({a: 1}, 'nooo why fail??').to.have.key('b');
     *
     * The alias `.key` can be used interchangeably with `.keys`.
     *
     * @name keys
     * @alias key
     * @param {...String|Array|Object} keys
     * @namespace BDD
     * @api public
     */

    function assertKeys (keys) {
      var obj = flag(this, 'object')
        , objType = _.type(obj)
        , keysType = _.type(keys)
        , ssfi = flag(this, 'ssfi')
        , isDeep = flag(this, 'deep')
        , str
        , deepStr = ''
        , ok = true
        , flagMsg = flag(this, 'message');

      flagMsg = flagMsg ? flagMsg + ': ' : '';
      var mixedArgsMsg = flagMsg + 'when testing keys against an object or an array you must give a single Array|Object|String argument or multiple String arguments';

      if (objType === 'Map' || objType === 'Set') {
        deepStr = isDeep ? 'deeply ' : '';
        actual = [];

        // Map and Set '.keys' aren't supported in IE 11. Therefore, use .forEach.
        obj.forEach(function (val, key) { actual.push(key) });

        if (keysType !== 'Array') {
          keys = Array.prototype.slice.call(arguments);
        }

      } else {
        actual = _.getOwnEnumerableProperties(obj);

        switch (keysType) {
          case 'Array':
            if (arguments.length > 1) {
              throw new AssertionError(mixedArgsMsg, undefined, ssfi);
            }
            break;
          case 'Object':
            if (arguments.length > 1) {
              throw new AssertionError(mixedArgsMsg, undefined, ssfi);
            }
            keys = Object.keys(keys);
            break;
          default:
            keys = Array.prototype.slice.call(arguments);
        }

        // Only stringify non-Symbols because Symbols would become "Symbol()"
        keys = keys.map(function (val) {
          return typeof val === 'symbol' ? val : String(val);
        });
      }

      if (!keys.length) {
        throw new AssertionError(flagMsg + 'keys required', undefined, ssfi);
      }

      var len = keys.length
        , any = flag(this, 'any')
        , all = flag(this, 'all')
        , expected = keys
        , actual;

      if (!any && !all) {
        all = true;
      }

      // Has any
      if (any) {
        ok = expected.some(function(expectedKey) {
          return actual.some(function(actualKey) {
            if (isDeep) {
              return _.eql(expectedKey, actualKey);
            } else {
              return expectedKey === actualKey;
            }
          });
        });
      }

      // Has all
      if (all) {
        ok = expected.every(function(expectedKey) {
          return actual.some(function(actualKey) {
            if (isDeep) {
              return _.eql(expectedKey, actualKey);
            } else {
              return expectedKey === actualKey;
            }
          });
        });

        if (!flag(this, 'contains')) {
          ok = ok && keys.length == actual.length;
        }
      }

      // Key string
      if (len > 1) {
        keys = keys.map(function(key) {
          return _.inspect(key);
        });
        var last = keys.pop();
        if (all) {
          str = keys.join(', ') + ', and ' + last;
        }
        if (any) {
          str = keys.join(', ') + ', or ' + last;
        }
      } else {
        str = _.inspect(keys[0]);
      }

      // Form
      str = (len > 1 ? 'keys ' : 'key ') + str;

      // Have / include
      str = (flag(this, 'contains') ? 'contain ' : 'have ') + str;

      // Assertion
      this.assert(
          ok
        , 'expected #{this} to ' + deepStr + str
        , 'expected #{this} to not ' + deepStr + str
        , expected.slice(0).sort(_.compareByInspect)
        , actual.sort(_.compareByInspect)
        , true
      );
    }

    Assertion.addMethod('keys', assertKeys);
    Assertion.addMethod('key', assertKeys);

    /**
     * ### .throw([errorLike], [errMsgMatcher], [msg])
     *
     * When no arguments are provided, `.throw` invokes the target function and
     * asserts that an error is thrown.
     *
     *     var badFn = function () { throw new TypeError('Illegal salmon!'); };
     *
     *     expect(badFn).to.throw();
     *
     * When one argument is provided, and it's an error constructor, `.throw`
     * invokes the target function and asserts that an error is thrown that's an
     * instance of that error constructor.
     *
     *     var badFn = function () { throw new TypeError('Illegal salmon!'); };
     *
     *     expect(badFn).to.throw(TypeError);
     *
     * When one argument is provided, and it's an error instance, `.throw` invokes
     * the target function and asserts that an error is thrown that's strictly
     * (`===`) equal to that error instance.
     *
     *     var err = new TypeError('Illegal salmon!');
     *     var badFn = function () { throw err; };
     *
     *     expect(badFn).to.throw(err);
     *
     * When one argument is provided, and it's a string, `.throw` invokes the
     * target function and asserts that an error is thrown with a message that
     * contains that string.
     *
     *     var badFn = function () { throw new TypeError('Illegal salmon!'); };
     *
     *     expect(badFn).to.throw('salmon');
     *
     * When one argument is provided, and it's a regular expression, `.throw`
     * invokes the target function and asserts that an error is thrown with a
     * message that matches that regular expression.
     *
     *     var badFn = function () { throw new TypeError('Illegal salmon!'); };
     *
     *     expect(badFn).to.throw(/salmon/);
     *
     * When two arguments are provided, and the first is an error instance or
     * constructor, and the second is a string or regular expression, `.throw`
     * invokes the function and asserts that an error is thrown that fulfills both
     * conditions as described above.
     *
     *     var err = new TypeError('Illegal salmon!');
     *     var badFn = function () { throw err; };
     *
     *     expect(badFn).to.throw(TypeError, 'salmon');
     *     expect(badFn).to.throw(TypeError, /salmon/);
     *     expect(badFn).to.throw(err, 'salmon');
     *     expect(badFn).to.throw(err, /salmon/);
     *
     * Add `.not` earlier in the chain to negate `.throw`.
     *
     *     var goodFn = function () {};
     *
     *     expect(goodFn).to.not.throw();
     *
     * However, it's dangerous to negate `.throw` when providing any arguments.
     * The problem is that it creates uncertain expectations by asserting that the
     * target either doesn't throw an error, or that it throws an error but of a
     * different type than the given type, or that it throws an error of the given
     * type but with a message that doesn't include the given string. It's often
     * best to identify the exact output that's expected, and then write an
     * assertion that only accepts that exact output.
     *
     * When the target isn't expected to throw an error, it's often best to assert
     * exactly that.
     *
     *     var goodFn = function () {};
     *
     *     expect(goodFn).to.not.throw(); // Recommended
     *     expect(goodFn).to.not.throw(ReferenceError, 'x'); // Not recommended
     *
     * When the target is expected to throw an error, it's often best to assert
     * that the error is of its expected type, and has a message that includes an
     * expected string, rather than asserting that it doesn't have one of many
     * unexpected types, and doesn't have a message that includes some string.
     *
     *     var badFn = function () { throw new TypeError('Illegal salmon!'); };
     *
     *     expect(badFn).to.throw(TypeError, 'salmon'); // Recommended
     *     expect(badFn).to.not.throw(ReferenceError, 'x'); // Not recommended
     *
     * `.throw` changes the target of any assertions that follow in the chain to
     * be the error object that's thrown.
     *
     *     var err = new TypeError('Illegal salmon!');
     *     err.code = 42;
     *     var badFn = function () { throw err; };
     *
     *     expect(badFn).to.throw(TypeError).with.property('code', 42);
     *
     * `.throw` accepts an optional `msg` argument which is a custom error message
     * to show when the assertion fails. The message can also be given as the
     * second argument to `expect`. When not providing two arguments, always use
     * the second form.
     *
     *     var goodFn = function () {};
     *
     *     expect(goodFn).to.throw(TypeError, 'x', 'nooo why fail??');
     *     expect(goodFn, 'nooo why fail??').to.throw();
     *
     * Due to limitations in ES5, `.throw` may not always work as expected when
     * using a transpiler such as Babel or TypeScript. In particular, it may
     * produce unexpected results when subclassing the built-in `Error` object and
     * then passing the subclassed constructor to `.throw`. See your transpiler's
     * docs for details:
     *
     * - ([Babel](https://babeljs.io/docs/usage/caveats/#classes))
     * - ([TypeScript](https://github.com/Microsoft/TypeScript/wiki/Breaking-Changes#extending-built-ins-like-error-array-and-map-may-no-longer-work))
     *
     * Beware of some common mistakes when using the `throw` assertion. One common
     * mistake is to accidentally invoke the function yourself instead of letting
     * the `throw` assertion invoke the function for you. For example, when
     * testing if a function named `fn` throws, provide `fn` instead of `fn()` as
     * the target for the assertion.
     *
     *     expect(fn).to.throw();     // Good! Tests `fn` as desired
     *     expect(fn()).to.throw();   // Bad! Tests result of `fn()`, not `fn`
     *
     * If you need to assert that your function `fn` throws when passed certain
     * arguments, then wrap a call to `fn` inside of another function.
     *
     *     expect(function () { fn(42); }).to.throw();  // Function expression
     *     expect(() => fn(42)).to.throw();             // ES6 arrow function
     *
     * Another common mistake is to provide an object method (or any stand-alone
     * function that relies on `this`) as the target of the assertion. Doing so is
     * problematic because the `this` context will be lost when the function is
     * invoked by `.throw`; there's no way for it to know what `this` is supposed
     * to be. There are two ways around this problem. One solution is to wrap the
     * method or function call inside of another function. Another solution is to
     * use `bind`.
     *
     *     expect(function () { cat.meow(); }).to.throw();  // Function expression
     *     expect(() => cat.meow()).to.throw();             // ES6 arrow function
     *     expect(cat.meow.bind(cat)).to.throw();           // Bind
     *
     * Finally, it's worth mentioning that it's a best practice in JavaScript to
     * only throw `Error` and derivatives of `Error` such as `ReferenceError`,
     * `TypeError`, and user-defined objects that extend `Error`. No other type of
     * value will generate a stack trace when initialized. With that said, the
     * `throw` assertion does technically support any type of value being thrown,
     * not just `Error` and its derivatives.
     *
     * The aliases `.throws` and `.Throw` can be used interchangeably with
     * `.throw`.
     *
     * @name throw
     * @alias throws
     * @alias Throw
     * @param {Error|ErrorConstructor} errorLike
     * @param {String|RegExp} errMsgMatcher error message
     * @param {String} msg _optional_
     * @see https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Error#Error_types
     * @returns error for chaining (null if no error)
     * @namespace BDD
     * @api public
     */

    function assertThrows (errorLike, errMsgMatcher, msg) {
      if (msg) flag(this, 'message', msg);
      var obj = flag(this, 'object')
        , ssfi = flag(this, 'ssfi')
        , flagMsg = flag(this, 'message')
        , negate = flag(this, 'negate') || false;
      new Assertion(obj, flagMsg, ssfi, true).is.a('function');

      if (errorLike instanceof RegExp || typeof errorLike === 'string') {
        errMsgMatcher = errorLike;
        errorLike = null;
      }

      var caughtErr;
      try {
        obj();
      } catch (err) {
        caughtErr = err;
      }

      // If we have the negate flag enabled and at least one valid argument it means we do expect an error
      // but we want it to match a given set of criteria
      var everyArgIsUndefined = errorLike === undefined && errMsgMatcher === undefined;

      // If we've got the negate flag enabled and both args, we should only fail if both aren't compatible
      // See Issue #551 and PR #683@GitHub
      var everyArgIsDefined = Boolean(errorLike && errMsgMatcher);
      var errorLikeFail = false;
      var errMsgMatcherFail = false;

      // Checking if error was thrown
      if (everyArgIsUndefined || !everyArgIsUndefined && !negate) {
        // We need this to display results correctly according to their types
        var errorLikeString = 'an error';
        if (errorLike instanceof Error) {
          errorLikeString = '#{exp}';
        } else if (errorLike) {
          errorLikeString = _.checkError.getConstructorName(errorLike);
        }

        this.assert(
            caughtErr
          , 'expected #{this} to throw ' + errorLikeString
          , 'expected #{this} to not throw an error but #{act} was thrown'
          , errorLike && errorLike.toString()
          , (caughtErr instanceof Error ?
              caughtErr.toString() : (typeof caughtErr === 'string' ? caughtErr : caughtErr &&
                                      _.checkError.getConstructorName(caughtErr)))
        );
      }

      if (errorLike && caughtErr) {
        // We should compare instances only if `errorLike` is an instance of `Error`
        if (errorLike instanceof Error) {
          var isCompatibleInstance = _.checkError.compatibleInstance(caughtErr, errorLike);

          if (isCompatibleInstance === negate) {
            // These checks were created to ensure we won't fail too soon when we've got both args and a negate
            // See Issue #551 and PR #683@GitHub
            if (everyArgIsDefined && negate) {
              errorLikeFail = true;
            } else {
              this.assert(
                  negate
                , 'expected #{this} to throw #{exp} but #{act} was thrown'
                , 'expected #{this} to not throw #{exp}' + (caughtErr && !negate ? ' but #{act} was thrown' : '')
                , errorLike.toString()
                , caughtErr.toString()
              );
            }
          }
        }

        var isCompatibleConstructor = _.checkError.compatibleConstructor(caughtErr, errorLike);
        if (isCompatibleConstructor === negate) {
          if (everyArgIsDefined && negate) {
              errorLikeFail = true;
          } else {
            this.assert(
                negate
              , 'expected #{this} to throw #{exp} but #{act} was thrown'
              , 'expected #{this} to not throw #{exp}' + (caughtErr ? ' but #{act} was thrown' : '')
              , (errorLike instanceof Error ? errorLike.toString() : errorLike && _.checkError.getConstructorName(errorLike))
              , (caughtErr instanceof Error ? caughtErr.toString() : caughtErr && _.checkError.getConstructorName(caughtErr))
            );
          }
        }
      }

      if (caughtErr && errMsgMatcher !== undefined && errMsgMatcher !== null) {
        // Here we check compatible messages
        var placeholder = 'including';
        if (errMsgMatcher instanceof RegExp) {
          placeholder = 'matching'
        }

        var isCompatibleMessage = _.checkError.compatibleMessage(caughtErr, errMsgMatcher);
        if (isCompatibleMessage === negate) {
          if (everyArgIsDefined && negate) {
              errMsgMatcherFail = true;
          } else {
            this.assert(
              negate
              , 'expected #{this} to throw error ' + placeholder + ' #{exp} but got #{act}'
              , 'expected #{this} to throw error not ' + placeholder + ' #{exp}'
              ,  errMsgMatcher
              ,  _.checkError.getMessage(caughtErr)
            );
          }
        }
      }

      // If both assertions failed and both should've matched we throw an error
      if (errorLikeFail && errMsgMatcherFail) {
        this.assert(
          negate
          , 'expected #{this} to throw #{exp} but #{act} was thrown'
          , 'expected #{this} to not throw #{exp}' + (caughtErr ? ' but #{act} was thrown' : '')
          , (errorLike instanceof Error ? errorLike.toString() : errorLike && _.checkError.getConstructorName(errorLike))
          , (caughtErr instanceof Error ? caughtErr.toString() : caughtErr && _.checkError.getConstructorName(caughtErr))
        );
      }

      flag(this, 'object', caughtErr);
    };

    Assertion.addMethod('throw', assertThrows);
    Assertion.addMethod('throws', assertThrows);
    Assertion.addMethod('Throw', assertThrows);

    /**
     * ### .respondTo(method[, msg])
     *
     * When the target is a non-function object, `.respondTo` asserts that the
     * target has a method with the given name `method`. The method can be own or
     * inherited, and it can be enumerable or non-enumerable.
     *
     *     function Cat () {}
     *     Cat.prototype.meow = function () {};
     *
     *     expect(new Cat()).to.respondTo('meow');
     *
     * When the target is a function, `.respondTo` asserts that the target's
     * `prototype` property has a method with the given name `method`. Again, the
     * method can be own or inherited, and it can be enumerable or non-enumerable.
     *
     *     function Cat () {}
     *     Cat.prototype.meow = function () {};
     *
     *     expect(Cat).to.respondTo('meow');
     *
     * Add `.itself` earlier in the chain to force `.respondTo` to treat the
     * target as a non-function object, even if it's a function. Thus, it asserts
     * that the target has a method with the given name `method`, rather than
     * asserting that the target's `prototype` property has a method with the
     * given name `method`.
     *
     *     function Cat () {}
     *     Cat.prototype.meow = function () {};
     *     Cat.hiss = function () {};
     *
     *     expect(Cat).itself.to.respondTo('hiss').but.not.respondTo('meow');
     *
     * When not adding `.itself`, it's important to check the target's type before
     * using `.respondTo`. See the `.a` doc for info on checking a target's type.
     *
     *     function Cat () {}
     *     Cat.prototype.meow = function () {};
     *
     *     expect(new Cat()).to.be.an('object').that.respondsTo('meow');
     *
     * Add `.not` earlier in the chain to negate `.respondTo`.
     *
     *     function Dog () {}
     *     Dog.prototype.bark = function () {};
     *
     *     expect(new Dog()).to.not.respondTo('meow');
     *
     * `.respondTo` accepts an optional `msg` argument which is a custom error
     * message to show when the assertion fails. The message can also be given as
     * the second argument to `expect`.
     *
     *     expect({}).to.respondTo('meow', 'nooo why fail??');
     *     expect({}, 'nooo why fail??').to.respondTo('meow');
     *
     * The alias `.respondsTo` can be used interchangeably with `.respondTo`.
     *
     * @name respondTo
     * @alias respondsTo
     * @param {String} method
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    function respondTo (method, msg) {
      if (msg) flag(this, 'message', msg);
      var obj = flag(this, 'object')
        , itself = flag(this, 'itself')
        , context = ('function' === typeof obj && !itself)
          ? obj.prototype[method]
          : obj[method];

      this.assert(
          'function' === typeof context
        , 'expected #{this} to respond to ' + _.inspect(method)
        , 'expected #{this} to not respond to ' + _.inspect(method)
      );
    }

    Assertion.addMethod('respondTo', respondTo);
    Assertion.addMethod('respondsTo', respondTo);

    /**
     * ### .itself
     *
     * Forces all `.respondTo` assertions that follow in the chain to behave as if
     * the target is a non-function object, even if it's a function. Thus, it
     * causes `.respondTo` to assert that the target has a method with the given
     * name, rather than asserting that the target's `prototype` property has a
     * method with the given name.
     *
     *     function Cat () {}
     *     Cat.prototype.meow = function () {};
     *     Cat.hiss = function () {};
     *
     *     expect(Cat).itself.to.respondTo('hiss').but.not.respondTo('meow');
     *
     * @name itself
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('itself', function () {
      flag(this, 'itself', true);
    });

    /**
     * ### .satisfy(matcher[, msg])
     *
     * Invokes the given `matcher` function with the target being passed as the
     * first argument, and asserts that the value returned is truthy.
     *
     *     expect(1).to.satisfy(function(num) {
     *       return num > 0;
     *     });
     *
     * Add `.not` earlier in the chain to negate `.satisfy`.
     *
     *     expect(1).to.not.satisfy(function(num) {
     *       return num > 2;
     *     });
     *
     * `.satisfy` accepts an optional `msg` argument which is a custom error
     * message to show when the assertion fails. The message can also be given as
     * the second argument to `expect`.
     *
     *     expect(1).to.satisfy(function(num) {
     *       return num > 2;
     *     }, 'nooo why fail??');
     *
     *     expect(1, 'nooo why fail??').to.satisfy(function(num) {
     *       return num > 2;
     *     });
     *
     * The alias `.satisfies` can be used interchangeably with `.satisfy`.
     *
     * @name satisfy
     * @alias satisfies
     * @param {Function} matcher
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    function satisfy (matcher, msg) {
      if (msg) flag(this, 'message', msg);
      var obj = flag(this, 'object');
      var result = matcher(obj);
      this.assert(
          result
        , 'expected #{this} to satisfy ' + _.objDisplay(matcher)
        , 'expected #{this} to not satisfy' + _.objDisplay(matcher)
        , flag(this, 'negate') ? false : true
        , result
      );
    }

    Assertion.addMethod('satisfy', satisfy);
    Assertion.addMethod('satisfies', satisfy);

    /**
     * ### .closeTo(expected, delta[, msg])
     *
     * Asserts that the target is a number that's within a given +/- `delta` range
     * of the given number `expected`. However, it's often best to assert that the
     * target is equal to its expected value.
     *
     *     // Recommended
     *     expect(1.5).to.equal(1.5);
     *
     *     // Not recommended
     *     expect(1.5).to.be.closeTo(1, 0.5);
     *     expect(1.5).to.be.closeTo(2, 0.5);
     *     expect(1.5).to.be.closeTo(1, 1);
     *
     * Add `.not` earlier in the chain to negate `.closeTo`.
     *
     *     expect(1.5).to.equal(1.5); // Recommended
     *     expect(1.5).to.not.be.closeTo(3, 1); // Not recommended
     *
     * `.closeTo` accepts an optional `msg` argument which is a custom error
     * message to show when the assertion fails. The message can also be given as
     * the second argument to `expect`.
     *
     *     expect(1.5).to.be.closeTo(3, 1, 'nooo why fail??');
     *     expect(1.5, 'nooo why fail??').to.be.closeTo(3, 1);
     *
     * The alias `.approximately` can be used interchangeably with `.closeTo`.
     *
     * @name closeTo
     * @alias approximately
     * @param {Number} expected
     * @param {Number} delta
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    function closeTo(expected, delta, msg) {
      if (msg) flag(this, 'message', msg);
      var obj = flag(this, 'object')
        , flagMsg = flag(this, 'message')
        , ssfi = flag(this, 'ssfi');

      new Assertion(obj, flagMsg, ssfi, true).is.a('number');
      if (typeof expected !== 'number' || typeof delta !== 'number') {
        flagMsg = flagMsg ? flagMsg + ': ' : '';
        throw new AssertionError(
            flagMsg + 'the arguments to closeTo or approximately must be numbers',
            undefined,
            ssfi
        );
      }

      this.assert(
          Math.abs(obj - expected) <= delta
        , 'expected #{this} to be close to ' + expected + ' +/- ' + delta
        , 'expected #{this} not to be close to ' + expected + ' +/- ' + delta
      );
    }

    Assertion.addMethod('closeTo', closeTo);
    Assertion.addMethod('approximately', closeTo);

    // Note: Duplicates are ignored if testing for inclusion instead of sameness.
    function isSubsetOf(subset, superset, cmp, contains, ordered) {
      if (!contains) {
        if (subset.length !== superset.length) return false;
        superset = superset.slice();
      }

      return subset.every(function(elem, idx) {
        if (ordered) return cmp ? cmp(elem, superset[idx]) : elem === superset[idx];

        if (!cmp) {
          var matchIdx = superset.indexOf(elem);
          if (matchIdx === -1) return false;

          // Remove match from superset so not counted twice if duplicate in subset.
          if (!contains) superset.splice(matchIdx, 1);
          return true;
        }

        return superset.some(function(elem2, matchIdx) {
          if (!cmp(elem, elem2)) return false;

          // Remove match from superset so not counted twice if duplicate in subset.
          if (!contains) superset.splice(matchIdx, 1);
          return true;
        });
      });
    }

    /**
     * ### .members(set[, msg])
     *
     * Asserts that the target array has the same members as the given array
     * `set`.
     *
     *     expect([1, 2, 3]).to.have.members([2, 1, 3]);
     *     expect([1, 2, 2]).to.have.members([2, 1, 2]);
     *
     * By default, members are compared using strict (`===`) equality. Add `.deep`
     * earlier in the chain to use deep equality instead. See the `deep-eql`
     * project page for info on the deep equality algorithm:
     * https://github.com/chaijs/deep-eql.
     *
     *     // Target array deeply (but not strictly) has member `{a: 1}`
     *     expect([{a: 1}]).to.have.deep.members([{a: 1}]);
     *     expect([{a: 1}]).to.not.have.members([{a: 1}]);
     *
     * By default, order doesn't matter. Add `.ordered` earlier in the chain to
     * require that members appear in the same order.
     *
     *     expect([1, 2, 3]).to.have.ordered.members([1, 2, 3]);
     *     expect([1, 2, 3]).to.have.members([2, 1, 3])
     *       .but.not.ordered.members([2, 1, 3]);
     *
     * By default, both arrays must be the same size. Add `.include` earlier in
     * the chain to require that the target's members be a superset of the
     * expected members. Note that duplicates are ignored in the subset when
     * `.include` is added.
     *
     *     // Target array is a superset of [1, 2] but not identical
     *     expect([1, 2, 3]).to.include.members([1, 2]);
     *     expect([1, 2, 3]).to.not.have.members([1, 2]);
     *
     *     // Duplicates in the subset are ignored
     *     expect([1, 2, 3]).to.include.members([1, 2, 2, 2]);
     *
     * `.deep`, `.ordered`, and `.include` can all be combined. However, if
     * `.include` and `.ordered` are combined, the ordering begins at the start of
     * both arrays.
     *
     *     expect([{a: 1}, {b: 2}, {c: 3}])
     *       .to.include.deep.ordered.members([{a: 1}, {b: 2}])
     *       .but.not.include.deep.ordered.members([{b: 2}, {c: 3}]);
     *
     * Add `.not` earlier in the chain to negate `.members`. However, it's
     * dangerous to do so. The problem is that it creates uncertain expectations
     * by asserting that the target array doesn't have all of the same members as
     * the given array `set` but may or may not have some of them. It's often best
     * to identify the exact output that's expected, and then write an assertion
     * that only accepts that exact output.
     *
     *     expect([1, 2]).to.not.include(3).and.not.include(4); // Recommended
     *     expect([1, 2]).to.not.have.members([3, 4]); // Not recommended
     *
     * `.members` accepts an optional `msg` argument which is a custom error
     * message to show when the assertion fails. The message can also be given as
     * the second argument to `expect`.
     *
     *     expect([1, 2]).to.have.members([1, 2, 3], 'nooo why fail??');
     *     expect([1, 2], 'nooo why fail??').to.have.members([1, 2, 3]);
     *
     * @name members
     * @param {Array} set
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    Assertion.addMethod('members', function (subset, msg) {
      if (msg) flag(this, 'message', msg);
      var obj = flag(this, 'object')
        , flagMsg = flag(this, 'message')
        , ssfi = flag(this, 'ssfi');

      new Assertion(obj, flagMsg, ssfi, true).to.be.an('array');
      new Assertion(subset, flagMsg, ssfi, true).to.be.an('array');

      var contains = flag(this, 'contains');
      var ordered = flag(this, 'ordered');

      var subject, failMsg, failNegateMsg, lengthCheck;

      if (contains) {
        subject = ordered ? 'an ordered superset' : 'a superset';
        failMsg = 'expected #{this} to be ' + subject + ' of #{exp}';
        failNegateMsg = 'expected #{this} to not be ' + subject + ' of #{exp}';
      } else {
        subject = ordered ? 'ordered members' : 'members';
        failMsg = 'expected #{this} to have the same ' + subject + ' as #{exp}';
        failNegateMsg = 'expected #{this} to not have the same ' + subject + ' as #{exp}';
      }

      var cmp = flag(this, 'deep') ? _.eql : undefined;

      this.assert(
          isSubsetOf(subset, obj, cmp, contains, ordered)
        , failMsg
        , failNegateMsg
        , subset
        , obj
        , true
      );
    });

    /**
     * ### .oneOf(list[, msg])
     *
     * Asserts that the target is a member of the given array `list`. However,
     * it's often best to assert that the target is equal to its expected value.
     *
     *     expect(1).to.equal(1); // Recommended
     *     expect(1).to.be.oneOf([1, 2, 3]); // Not recommended
     *
     * Comparisons are performed using strict (`===`) equality.
     *
     * Add `.not` earlier in the chain to negate `.oneOf`.
     *
     *     expect(1).to.equal(1); // Recommended
     *     expect(1).to.not.be.oneOf([2, 3, 4]); // Not recommended
     *
     * `.oneOf` accepts an optional `msg` argument which is a custom error message
     * to show when the assertion fails. The message can also be given as the
     * second argument to `expect`.
     *
     *     expect(1).to.be.oneOf([2, 3, 4], 'nooo why fail??');
     *     expect(1, 'nooo why fail??').to.be.oneOf([2, 3, 4]);
     *
     * @name oneOf
     * @param {Array<*>} list
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    function oneOf (list, msg) {
      if (msg) flag(this, 'message', msg);
      var expected = flag(this, 'object')
        , flagMsg = flag(this, 'message')
        , ssfi = flag(this, 'ssfi');
      new Assertion(list, flagMsg, ssfi, true).to.be.an('array');

      this.assert(
          list.indexOf(expected) > -1
        , 'expected #{this} to be one of #{exp}'
        , 'expected #{this} to not be one of #{exp}'
        , list
        , expected
      );
    }

    Assertion.addMethod('oneOf', oneOf);


    /**
     * ### .change(subject[, prop[, msg]])
     *
     * When one argument is provided, `.change` asserts that the given function
     * `subject` returns a different value when it's invoked before the target
     * function compared to when it's invoked afterward. However, it's often best
     * to assert that `subject` is equal to its expected value.
     *
     *     var dots = ''
     *       , addDot = function () { dots += '.'; }
     *       , getDots = function () { return dots; };
     *
     *     // Recommended
     *     expect(getDots()).to.equal('');
     *     addDot();
     *     expect(getDots()).to.equal('.');
     *
     *     // Not recommended
     *     expect(addDot).to.change(getDots);
     *
     * When two arguments are provided, `.change` asserts that the value of the
     * given object `subject`'s `prop` property is different before invoking the
     * target function compared to afterward.
     *
     *     var myObj = {dots: ''}
     *       , addDot = function () { myObj.dots += '.'; };
     *
     *     // Recommended
     *     expect(myObj).to.have.property('dots', '');
     *     addDot();
     *     expect(myObj).to.have.property('dots', '.');
     *
     *     // Not recommended
     *     expect(addDot).to.change(myObj, 'dots');
     *
     * Strict (`===`) equality is used to compare before and after values.
     *
     * Add `.not` earlier in the chain to negate `.change`.
     *
     *     var dots = ''
     *       , noop = function () {}
     *       , getDots = function () { return dots; };
     *
     *     expect(noop).to.not.change(getDots);
     *
     *     var myObj = {dots: ''}
     *       , noop = function () {};
     *
     *     expect(noop).to.not.change(myObj, 'dots');
     *
     * `.change` accepts an optional `msg` argument which is a custom error
     * message to show when the assertion fails. The message can also be given as
     * the second argument to `expect`. When not providing two arguments, always
     * use the second form.
     *
     *     var myObj = {dots: ''}
     *       , addDot = function () { myObj.dots += '.'; };
     *
     *     expect(addDot).to.not.change(myObj, 'dots', 'nooo why fail??');
     *
     *     var dots = ''
     *       , addDot = function () { dots += '.'; }
     *       , getDots = function () { return dots; };
     *
     *     expect(addDot, 'nooo why fail??').to.not.change(getDots);
     *
     * `.change` also causes all `.by` assertions that follow in the chain to
     * assert how much a numeric subject was increased or decreased by. However,
     * it's dangerous to use `.change.by`. The problem is that it creates
     * uncertain expectations by asserting that the subject either increases by
     * the given delta, or that it decreases by the given delta. It's often best
     * to identify the exact output that's expected, and then write an assertion
     * that only accepts that exact output.
     *
     *     var myObj = {val: 1}
     *       , addTwo = function () { myObj.val += 2; }
     *       , subtractTwo = function () { myObj.val -= 2; };
     *
     *     expect(addTwo).to.increase(myObj, 'val').by(2); // Recommended
     *     expect(addTwo).to.change(myObj, 'val').by(2); // Not recommended
     *
     *     expect(subtractTwo).to.decrease(myObj, 'val').by(2); // Recommended
     *     expect(subtractTwo).to.change(myObj, 'val').by(2); // Not recommended
     *
     * The alias `.changes` can be used interchangeably with `.change`.
     *
     * @name change
     * @alias changes
     * @param {String} subject
     * @param {String} prop name _optional_
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    function assertChanges (subject, prop, msg) {
      if (msg) flag(this, 'message', msg);
      var fn = flag(this, 'object')
        , flagMsg = flag(this, 'message')
        , ssfi = flag(this, 'ssfi');
      new Assertion(fn, flagMsg, ssfi, true).is.a('function');

      var initial;
      if (!prop) {
        new Assertion(subject, flagMsg, ssfi, true).is.a('function');
        initial = subject();
      } else {
        new Assertion(subject, flagMsg, ssfi, true).to.have.property(prop);
        initial = subject[prop];
      }

      fn();

      var final = prop === undefined || prop === null ? subject() : subject[prop];
      var msgObj = prop === undefined || prop === null ? initial : '.' + prop;

      // This gets flagged because of the .by(delta) assertion
      flag(this, 'deltaMsgObj', msgObj);
      flag(this, 'initialDeltaValue', initial);
      flag(this, 'finalDeltaValue', final);
      flag(this, 'deltaBehavior', 'change');
      flag(this, 'realDelta', final !== initial);

      this.assert(
        initial !== final
        , 'expected ' + msgObj + ' to change'
        , 'expected ' + msgObj + ' to not change'
      );
    }

    Assertion.addMethod('change', assertChanges);
    Assertion.addMethod('changes', assertChanges);

    /**
     * ### .increase(subject[, prop[, msg]])
     *
     * When one argument is provided, `.increase` asserts that the given function
     * `subject` returns a greater number when it's invoked after invoking the
     * target function compared to when it's invoked beforehand. `.increase` also
     * causes all `.by` assertions that follow in the chain to assert how much
     * greater of a number is returned. It's often best to assert that the return
     * value increased by the expected amount, rather than asserting it increased
     * by any amount.
     *
     *     var val = 1
     *       , addTwo = function () { val += 2; }
     *       , getVal = function () { return val; };
     *
     *     expect(addTwo).to.increase(getVal).by(2); // Recommended
     *     expect(addTwo).to.increase(getVal); // Not recommended
     *
     * When two arguments are provided, `.increase` asserts that the value of the
     * given object `subject`'s `prop` property is greater after invoking the
     * target function compared to beforehand.
     *
     *     var myObj = {val: 1}
     *       , addTwo = function () { myObj.val += 2; };
     *
     *     expect(addTwo).to.increase(myObj, 'val').by(2); // Recommended
     *     expect(addTwo).to.increase(myObj, 'val'); // Not recommended
     *
     * Add `.not` earlier in the chain to negate `.increase`. However, it's
     * dangerous to do so. The problem is that it creates uncertain expectations
     * by asserting that the subject either decreases, or that it stays the same.
     * It's often best to identify the exact output that's expected, and then
     * write an assertion that only accepts that exact output.
     *
     * When the subject is expected to decrease, it's often best to assert that it
     * decreased by the expected amount.
     *
     *     var myObj = {val: 1}
     *       , subtractTwo = function () { myObj.val -= 2; };
     *
     *     expect(subtractTwo).to.decrease(myObj, 'val').by(2); // Recommended
     *     expect(subtractTwo).to.not.increase(myObj, 'val'); // Not recommended
     *
     * When the subject is expected to stay the same, it's often best to assert
     * exactly that.
     *
     *     var myObj = {val: 1}
     *       , noop = function () {};
     *
     *     expect(noop).to.not.change(myObj, 'val'); // Recommended
     *     expect(noop).to.not.increase(myObj, 'val'); // Not recommended
     *
     * `.increase` accepts an optional `msg` argument which is a custom error
     * message to show when the assertion fails. The message can also be given as
     * the second argument to `expect`. When not providing two arguments, always
     * use the second form.
     *
     *     var myObj = {val: 1}
     *       , noop = function () {};
     *
     *     expect(noop).to.increase(myObj, 'val', 'nooo why fail??');
     *
     *     var val = 1
     *       , noop = function () {}
     *       , getVal = function () { return val; };
     *
     *     expect(noop, 'nooo why fail??').to.increase(getVal);
     *
     * The alias `.increases` can be used interchangeably with `.increase`.
     *
     * @name increase
     * @alias increases
     * @param {String|Function} subject
     * @param {String} prop name _optional_
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    function assertIncreases (subject, prop, msg) {
      if (msg) flag(this, 'message', msg);
      var fn = flag(this, 'object')
        , flagMsg = flag(this, 'message')
        , ssfi = flag(this, 'ssfi');
      new Assertion(fn, flagMsg, ssfi, true).is.a('function');

      var initial;
      if (!prop) {
        new Assertion(subject, flagMsg, ssfi, true).is.a('function');
        initial = subject();
      } else {
        new Assertion(subject, flagMsg, ssfi, true).to.have.property(prop);
        initial = subject[prop];
      }

      // Make sure that the target is a number
      new Assertion(initial, flagMsg, ssfi, true).is.a('number');

      fn();

      var final = prop === undefined || prop === null ? subject() : subject[prop];
      var msgObj = prop === undefined || prop === null ? initial : '.' + prop;

      flag(this, 'deltaMsgObj', msgObj);
      flag(this, 'initialDeltaValue', initial);
      flag(this, 'finalDeltaValue', final);
      flag(this, 'deltaBehavior', 'increase');
      flag(this, 'realDelta', final - initial);

      this.assert(
        final - initial > 0
        , 'expected ' + msgObj + ' to increase'
        , 'expected ' + msgObj + ' to not increase'
      );
    }

    Assertion.addMethod('increase', assertIncreases);
    Assertion.addMethod('increases', assertIncreases);

    /**
     * ### .decrease(subject[, prop[, msg]])
     *
     * When one argument is provided, `.decrease` asserts that the given function
     * `subject` returns a lesser number when it's invoked after invoking the
     * target function compared to when it's invoked beforehand. `.decrease` also
     * causes all `.by` assertions that follow in the chain to assert how much
     * lesser of a number is returned. It's often best to assert that the return
     * value decreased by the expected amount, rather than asserting it decreased
     * by any amount.
     *
     *     var val = 1
     *       , subtractTwo = function () { val -= 2; }
     *       , getVal = function () { return val; };
     *
     *     expect(subtractTwo).to.decrease(getVal).by(2); // Recommended
     *     expect(subtractTwo).to.decrease(getVal); // Not recommended
     *
     * When two arguments are provided, `.decrease` asserts that the value of the
     * given object `subject`'s `prop` property is lesser after invoking the
     * target function compared to beforehand.
     *
     *     var myObj = {val: 1}
     *       , subtractTwo = function () { myObj.val -= 2; };
     *
     *     expect(subtractTwo).to.decrease(myObj, 'val').by(2); // Recommended
     *     expect(subtractTwo).to.decrease(myObj, 'val'); // Not recommended
     *
     * Add `.not` earlier in the chain to negate `.decrease`. However, it's
     * dangerous to do so. The problem is that it creates uncertain expectations
     * by asserting that the subject either increases, or that it stays the same.
     * It's often best to identify the exact output that's expected, and then
     * write an assertion that only accepts that exact output.
     *
     * When the subject is expected to increase, it's often best to assert that it
     * increased by the expected amount.
     *
     *     var myObj = {val: 1}
     *       , addTwo = function () { myObj.val += 2; };
     *
     *     expect(addTwo).to.increase(myObj, 'val').by(2); // Recommended
     *     expect(addTwo).to.not.decrease(myObj, 'val'); // Not recommended
     *
     * When the subject is expected to stay the same, it's often best to assert
     * exactly that.
     *
     *     var myObj = {val: 1}
     *       , noop = function () {};
     *
     *     expect(noop).to.not.change(myObj, 'val'); // Recommended
     *     expect(noop).to.not.decrease(myObj, 'val'); // Not recommended
     *
     * `.decrease` accepts an optional `msg` argument which is a custom error
     * message to show when the assertion fails. The message can also be given as
     * the second argument to `expect`. When not providing two arguments, always
     * use the second form.
     *
     *     var myObj = {val: 1}
     *       , noop = function () {};
     *
     *     expect(noop).to.decrease(myObj, 'val', 'nooo why fail??');
     *
     *     var val = 1
     *       , noop = function () {}
     *       , getVal = function () { return val; };
     *
     *     expect(noop, 'nooo why fail??').to.decrease(getVal);
     *
     * The alias `.decreases` can be used interchangeably with `.decrease`.
     *
     * @name decrease
     * @alias decreases
     * @param {String|Function} subject
     * @param {String} prop name _optional_
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    function assertDecreases (subject, prop, msg) {
      if (msg) flag(this, 'message', msg);
      var fn = flag(this, 'object')
        , flagMsg = flag(this, 'message')
        , ssfi = flag(this, 'ssfi');
      new Assertion(fn, flagMsg, ssfi, true).is.a('function');

      var initial;
      if (!prop) {
        new Assertion(subject, flagMsg, ssfi, true).is.a('function');
        initial = subject();
      } else {
        new Assertion(subject, flagMsg, ssfi, true).to.have.property(prop);
        initial = subject[prop];
      }

      // Make sure that the target is a number
      new Assertion(initial, flagMsg, ssfi, true).is.a('number');

      fn();

      var final = prop === undefined || prop === null ? subject() : subject[prop];
      var msgObj = prop === undefined || prop === null ? initial : '.' + prop;

      flag(this, 'deltaMsgObj', msgObj);
      flag(this, 'initialDeltaValue', initial);
      flag(this, 'finalDeltaValue', final);
      flag(this, 'deltaBehavior', 'decrease');
      flag(this, 'realDelta', initial - final);

      this.assert(
        final - initial < 0
        , 'expected ' + msgObj + ' to decrease'
        , 'expected ' + msgObj + ' to not decrease'
      );
    }

    Assertion.addMethod('decrease', assertDecreases);
    Assertion.addMethod('decreases', assertDecreases);

    /**
     * ### .by(delta[, msg])
     *
     * When following an `.increase` assertion in the chain, `.by` asserts that
     * the subject of the `.increase` assertion increased by the given `delta`.
     *
     *     var myObj = {val: 1}
     *       , addTwo = function () { myObj.val += 2; };
     *
     *     expect(addTwo).to.increase(myObj, 'val').by(2);
     *
     * When following a `.decrease` assertion in the chain, `.by` asserts that the
     * subject of the `.decrease` assertion decreased by the given `delta`.
     *
     *     var myObj = {val: 1}
     *       , subtractTwo = function () { myObj.val -= 2; };
     *
     *     expect(subtractTwo).to.decrease(myObj, 'val').by(2);
     *
     * When following a `.change` assertion in the chain, `.by` asserts that the
     * subject of the `.change` assertion either increased or decreased by the
     * given `delta`. However, it's dangerous to use `.change.by`. The problem is
     * that it creates uncertain expectations. It's often best to identify the
     * exact output that's expected, and then write an assertion that only accepts
     * that exact output.
     *
     *     var myObj = {val: 1}
     *       , addTwo = function () { myObj.val += 2; }
     *       , subtractTwo = function () { myObj.val -= 2; };
     *
     *     expect(addTwo).to.increase(myObj, 'val').by(2); // Recommended
     *     expect(addTwo).to.change(myObj, 'val').by(2); // Not recommended
     *
     *     expect(subtractTwo).to.decrease(myObj, 'val').by(2); // Recommended
     *     expect(subtractTwo).to.change(myObj, 'val').by(2); // Not recommended
     *
     * Add `.not` earlier in the chain to negate `.by`. However, it's often best
     * to assert that the subject changed by its expected delta, rather than
     * asserting that it didn't change by one of countless unexpected deltas.
     *
     *     var myObj = {val: 1}
     *       , addTwo = function () { myObj.val += 2; };
     *
     *     // Recommended
     *     expect(addTwo).to.increase(myObj, 'val').by(2);
     *
     *     // Not recommended
     *     expect(addTwo).to.increase(myObj, 'val').but.not.by(3);
     *
     * `.by` accepts an optional `msg` argument which is a custom error message to
     * show when the assertion fails. The message can also be given as the second
     * argument to `expect`.
     *
     *     var myObj = {val: 1}
     *       , addTwo = function () { myObj.val += 2; };
     *
     *     expect(addTwo).to.increase(myObj, 'val').by(3, 'nooo why fail??');
     *     expect(addTwo, 'nooo why fail??').to.increase(myObj, 'val').by(3);
     *
     * @name by
     * @param {Number} delta
     * @param {String} msg _optional_
     * @namespace BDD
     * @api public
     */

    function assertDelta(delta, msg) {
      if (msg) flag(this, 'message', msg);

      var msgObj = flag(this, 'deltaMsgObj');
      var initial = flag(this, 'initialDeltaValue');
      var final = flag(this, 'finalDeltaValue');
      var behavior = flag(this, 'deltaBehavior');
      var realDelta = flag(this, 'realDelta');

      var expression;
      if (behavior === 'change') {
        expression = Math.abs(final - initial) === Math.abs(delta);
      } else {
        expression = realDelta === Math.abs(delta);
      }

      this.assert(
        expression
        , 'expected ' + msgObj + ' to ' + behavior + ' by ' + delta
        , 'expected ' + msgObj + ' to not ' + behavior + ' by ' + delta
      );
    }

    Assertion.addMethod('by', assertDelta);

    /**
     * ### .extensible
     *
     * Asserts that the target is extensible, which means that new properties can
     * be added to it. Primitives are never extensible.
     *
     *     expect({a: 1}).to.be.extensible;
     *
     * Add `.not` earlier in the chain to negate `.extensible`.
     *
     *     var nonExtensibleObject = Object.preventExtensions({})
     *       , sealedObject = Object.seal({})
     *       , frozenObject = Object.freeze({});
     *
     *     expect(nonExtensibleObject).to.not.be.extensible;
     *     expect(sealedObject).to.not.be.extensible;
     *     expect(frozenObject).to.not.be.extensible;
     *     expect(1).to.not.be.extensible;
     *
     * A custom error message can be given as the second argument to `expect`.
     *
     *     expect(1, 'nooo why fail??').to.be.extensible;
     *
     * @name extensible
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('extensible', function() {
      var obj = flag(this, 'object');

      // In ES5, if the argument to this method is a primitive, then it will cause a TypeError.
      // In ES6, a non-object argument will be treated as if it was a non-extensible ordinary object, simply return false.
      // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isExtensible
      // The following provides ES6 behavior for ES5 environments.

      var isExtensible = obj === Object(obj) && Object.isExtensible(obj);

      this.assert(
        isExtensible
        , 'expected #{this} to be extensible'
        , 'expected #{this} to not be extensible'
      );
    });

    /**
     * ### .sealed
     *
     * Asserts that the target is sealed, which means that new properties can't be
     * added to it, and its existing properties can't be reconfigured or deleted.
     * However, it's possible that its existing properties can still be reassigned
     * to different values. Primitives are always sealed.
     *
     *     var sealedObject = Object.seal({});
     *     var frozenObject = Object.freeze({});
     *
     *     expect(sealedObject).to.be.sealed;
     *     expect(frozenObject).to.be.sealed;
     *     expect(1).to.be.sealed;
     *
     * Add `.not` earlier in the chain to negate `.sealed`.
     *
     *     expect({a: 1}).to.not.be.sealed;
     *
     * A custom error message can be given as the second argument to `expect`.
     *
     *     expect({a: 1}, 'nooo why fail??').to.be.sealed;
     *
     * @name sealed
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('sealed', function() {
      var obj = flag(this, 'object');

      // In ES5, if the argument to this method is a primitive, then it will cause a TypeError.
      // In ES6, a non-object argument will be treated as if it was a sealed ordinary object, simply return true.
      // See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isSealed
      // The following provides ES6 behavior for ES5 environments.

      var isSealed = obj === Object(obj) ? Object.isSealed(obj) : true;

      this.assert(
        isSealed
        , 'expected #{this} to be sealed'
        , 'expected #{this} to not be sealed'
      );
    });

    /**
     * ### .frozen
     *
     * Asserts that the target is frozen, which means that new properties can't be
     * added to it, and its existing properties can't be reassigned to different
     * values, reconfigured, or deleted. Primitives are always frozen.
     *
     *     var frozenObject = Object.freeze({});
     *
     *     expect(frozenObject).to.be.frozen;
     *     expect(1).to.be.frozen;
     *
     * Add `.not` earlier in the chain to negate `.frozen`.
     *
     *     expect({a: 1}).to.not.be.frozen;
     *
     * A custom error message can be given as the second argument to `expect`.
     *
     *     expect({a: 1}, 'nooo why fail??').to.be.frozen;
     *
     * @name frozen
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('frozen', function() {
      var obj = flag(this, 'object');

      // In ES5, if the argument to this method is a primitive, then it will cause a TypeError.
      // In ES6, a non-object argument will be treated as if it was a frozen ordinary object, simply return true.
      // See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isFrozen
      // The following provides ES6 behavior for ES5 environments.

      var isFrozen = obj === Object(obj) ? Object.isFrozen(obj) : true;

      this.assert(
        isFrozen
        , 'expected #{this} to be frozen'
        , 'expected #{this} to not be frozen'
      );
    });

    /**
     * ### .finite
     *
     * Asserts that the target is a number, and isn't `NaN` or positive/negative
     * `Infinity`.
     *
     *     expect(1).to.be.finite;
     *
     * Add `.not` earlier in the chain to negate `.finite`. However, it's
     * dangerous to do so. The problem is that it creates uncertain expectations
     * by asserting that the subject either isn't a number, or that it's `NaN`, or
     * that it's positive `Infinity`, or that it's negative `Infinity`. It's often
     * best to identify the exact output that's expected, and then write an
     * assertion that only accepts that exact output.
     *
     * When the target isn't expected to be a number, it's often best to assert
     * that it's the expected type, rather than asserting that it isn't one of
     * many unexpected types.
     *
     *     expect('foo').to.be.a('string'); // Recommended
     *     expect('foo').to.not.be.finite; // Not recommended
     *
     * When the target is expected to be `NaN`, it's often best to assert exactly
     * that.
     *
     *     expect(NaN).to.be.NaN; // Recommended
     *     expect(NaN).to.not.be.finite; // Not recommended
     *
     * When the target is expected to be positive infinity, it's often best to
     * assert exactly that.
     *
     *     expect(Infinity).to.equal(Infinity); // Recommended
     *     expect(Infinity).to.not.be.finite; // Not recommended
     *
     * When the target is expected to be negative infinity, it's often best to
     * assert exactly that.
     *
     *     expect(-Infinity).to.equal(-Infinity); // Recommended
     *     expect(-Infinity).to.not.be.finite; // Not recommended
     *
     * A custom error message can be given as the second argument to `expect`.
     *
     *     expect('foo', 'nooo why fail??').to.be.finite;
     *
     * @name finite
     * @namespace BDD
     * @api public
     */

    Assertion.addProperty('finite', function(msg) {
      var obj = flag(this, 'object');

      this.assert(
          typeof obj === "number" && isFinite(obj)
        , 'expected #{this} to be a finite number'
        , 'expected #{this} to not be a finite number'
      );
    });
  };

  },{}],6:[function(require,module,exports){
  /*!
   * chai
   * Copyright(c) 2011-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */


  module.exports = function (chai, util) {

    /*!
     * Chai dependencies.
     */

    var Assertion = chai.Assertion
      , flag = util.flag;

    /*!
     * Module export.
     */

    /**
     * ### assert(expression, message)
     *
     * Write your own test expressions.
     *
     *     assert('foo' !== 'bar', 'foo is not bar');
     *     assert(Array.isArray([]), 'empty arrays are arrays');
     *
     * @param {Mixed} expression to test for truthiness
     * @param {String} message to display on error
     * @name assert
     * @namespace Assert
     * @api public
     */

    var assert = chai.assert = function (express, errmsg) {
      var test = new Assertion(null, null, chai.assert, true);
      test.assert(
          express
        , errmsg
        , '[ negation message unavailable ]'
      );
    };

    /**
     * ### .fail(actual, expected, [message], [operator])
     *
     * Throw a failure. Node.js `assert` module-compatible.
     *
     * @name fail
     * @param {Mixed} actual
     * @param {Mixed} expected
     * @param {String} message
     * @param {String} operator
     * @namespace Assert
     * @api public
     */

    assert.fail = function (actual, expected, message, operator) {
      message = message || 'assert.fail()';
      throw new chai.AssertionError(message, {
          actual: actual
        , expected: expected
        , operator: operator
      }, assert.fail);
    };

    /**
     * ### .isOk(object, [message])
     *
     * Asserts that `object` is truthy.
     *
     *     assert.isOk('everything', 'everything is ok');
     *     assert.isOk(false, 'this will fail');
     *
     * @name isOk
     * @alias ok
     * @param {Mixed} object to test
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isOk = function (val, msg) {
      new Assertion(val, msg, assert.isOk, true).is.ok;
    };

    /**
     * ### .isNotOk(object, [message])
     *
     * Asserts that `object` is falsy.
     *
     *     assert.isNotOk('everything', 'this will fail');
     *     assert.isNotOk(false, 'this will pass');
     *
     * @name isNotOk
     * @alias notOk
     * @param {Mixed} object to test
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isNotOk = function (val, msg) {
      new Assertion(val, msg, assert.isNotOk, true).is.not.ok;
    };

    /**
     * ### .equal(actual, expected, [message])
     *
     * Asserts non-strict equality (`==`) of `actual` and `expected`.
     *
     *     assert.equal(3, '3', '== coerces values to strings');
     *
     * @name equal
     * @param {Mixed} actual
     * @param {Mixed} expected
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.equal = function (act, exp, msg) {
      var test = new Assertion(act, msg, assert.equal, true);

      test.assert(
          exp == flag(test, 'object')
        , 'expected #{this} to equal #{exp}'
        , 'expected #{this} to not equal #{act}'
        , exp
        , act
        , true
      );
    };

    /**
     * ### .notEqual(actual, expected, [message])
     *
     * Asserts non-strict inequality (`!=`) of `actual` and `expected`.
     *
     *     assert.notEqual(3, 4, 'these numbers are not equal');
     *
     * @name notEqual
     * @param {Mixed} actual
     * @param {Mixed} expected
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notEqual = function (act, exp, msg) {
      var test = new Assertion(act, msg, assert.notEqual, true);

      test.assert(
          exp != flag(test, 'object')
        , 'expected #{this} to not equal #{exp}'
        , 'expected #{this} to equal #{act}'
        , exp
        , act
        , true
      );
    };

    /**
     * ### .strictEqual(actual, expected, [message])
     *
     * Asserts strict equality (`===`) of `actual` and `expected`.
     *
     *     assert.strictEqual(true, true, 'these booleans are strictly equal');
     *
     * @name strictEqual
     * @param {Mixed} actual
     * @param {Mixed} expected
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.strictEqual = function (act, exp, msg) {
      new Assertion(act, msg, assert.strictEqual, true).to.equal(exp);
    };

    /**
     * ### .notStrictEqual(actual, expected, [message])
     *
     * Asserts strict inequality (`!==`) of `actual` and `expected`.
     *
     *     assert.notStrictEqual(3, '3', 'no coercion for strict equality');
     *
     * @name notStrictEqual
     * @param {Mixed} actual
     * @param {Mixed} expected
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notStrictEqual = function (act, exp, msg) {
      new Assertion(act, msg, assert.notStrictEqual, true).to.not.equal(exp);
    };

    /**
     * ### .deepEqual(actual, expected, [message])
     *
     * Asserts that `actual` is deeply equal to `expected`.
     *
     *     assert.deepEqual({ tea: 'green' }, { tea: 'green' });
     *
     * @name deepEqual
     * @param {Mixed} actual
     * @param {Mixed} expected
     * @param {String} message
     * @alias deepStrictEqual
     * @namespace Assert
     * @api public
     */

    assert.deepEqual = assert.deepStrictEqual = function (act, exp, msg) {
      new Assertion(act, msg, assert.deepEqual, true).to.eql(exp);
    };

    /**
     * ### .notDeepEqual(actual, expected, [message])
     *
     * Assert that `actual` is not deeply equal to `expected`.
     *
     *     assert.notDeepEqual({ tea: 'green' }, { tea: 'jasmine' });
     *
     * @name notDeepEqual
     * @param {Mixed} actual
     * @param {Mixed} expected
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notDeepEqual = function (act, exp, msg) {
      new Assertion(act, msg, assert.notDeepEqual, true).to.not.eql(exp);
    };

     /**
     * ### .isAbove(valueToCheck, valueToBeAbove, [message])
     *
     * Asserts `valueToCheck` is strictly greater than (>) `valueToBeAbove`.
     *
     *     assert.isAbove(5, 2, '5 is strictly greater than 2');
     *
     * @name isAbove
     * @param {Mixed} valueToCheck
     * @param {Mixed} valueToBeAbove
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isAbove = function (val, abv, msg) {
      new Assertion(val, msg, assert.isAbove, true).to.be.above(abv);
    };

     /**
     * ### .isAtLeast(valueToCheck, valueToBeAtLeast, [message])
     *
     * Asserts `valueToCheck` is greater than or equal to (>=) `valueToBeAtLeast`.
     *
     *     assert.isAtLeast(5, 2, '5 is greater or equal to 2');
     *     assert.isAtLeast(3, 3, '3 is greater or equal to 3');
     *
     * @name isAtLeast
     * @param {Mixed} valueToCheck
     * @param {Mixed} valueToBeAtLeast
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isAtLeast = function (val, atlst, msg) {
      new Assertion(val, msg, assert.isAtLeast, true).to.be.least(atlst);
    };

     /**
     * ### .isBelow(valueToCheck, valueToBeBelow, [message])
     *
     * Asserts `valueToCheck` is strictly less than (<) `valueToBeBelow`.
     *
     *     assert.isBelow(3, 6, '3 is strictly less than 6');
     *
     * @name isBelow
     * @param {Mixed} valueToCheck
     * @param {Mixed} valueToBeBelow
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isBelow = function (val, blw, msg) {
      new Assertion(val, msg, assert.isBelow, true).to.be.below(blw);
    };

     /**
     * ### .isAtMost(valueToCheck, valueToBeAtMost, [message])
     *
     * Asserts `valueToCheck` is less than or equal to (<=) `valueToBeAtMost`.
     *
     *     assert.isAtMost(3, 6, '3 is less than or equal to 6');
     *     assert.isAtMost(4, 4, '4 is less than or equal to 4');
     *
     * @name isAtMost
     * @param {Mixed} valueToCheck
     * @param {Mixed} valueToBeAtMost
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isAtMost = function (val, atmst, msg) {
      new Assertion(val, msg, assert.isAtMost, true).to.be.most(atmst);
    };

    /**
     * ### .isTrue(value, [message])
     *
     * Asserts that `value` is true.
     *
     *     var teaServed = true;
     *     assert.isTrue(teaServed, 'the tea has been served');
     *
     * @name isTrue
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isTrue = function (val, msg) {
      new Assertion(val, msg, assert.isTrue, true).is['true'];
    };

    /**
     * ### .isNotTrue(value, [message])
     *
     * Asserts that `value` is not true.
     *
     *     var tea = 'tasty chai';
     *     assert.isNotTrue(tea, 'great, time for tea!');
     *
     * @name isNotTrue
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isNotTrue = function (val, msg) {
      new Assertion(val, msg, assert.isNotTrue, true).to.not.equal(true);
    };

    /**
     * ### .isFalse(value, [message])
     *
     * Asserts that `value` is false.
     *
     *     var teaServed = false;
     *     assert.isFalse(teaServed, 'no tea yet? hmm...');
     *
     * @name isFalse
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isFalse = function (val, msg) {
      new Assertion(val, msg, assert.isFalse, true).is['false'];
    };

    /**
     * ### .isNotFalse(value, [message])
     *
     * Asserts that `value` is not false.
     *
     *     var tea = 'tasty chai';
     *     assert.isNotFalse(tea, 'great, time for tea!');
     *
     * @name isNotFalse
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isNotFalse = function (val, msg) {
      new Assertion(val, msg, assert.isNotFalse, true).to.not.equal(false);
    };

    /**
     * ### .isNull(value, [message])
     *
     * Asserts that `value` is null.
     *
     *     assert.isNull(err, 'there was no error');
     *
     * @name isNull
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isNull = function (val, msg) {
      new Assertion(val, msg, assert.isNull, true).to.equal(null);
    };

    /**
     * ### .isNotNull(value, [message])
     *
     * Asserts that `value` is not null.
     *
     *     var tea = 'tasty chai';
     *     assert.isNotNull(tea, 'great, time for tea!');
     *
     * @name isNotNull
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isNotNull = function (val, msg) {
      new Assertion(val, msg, assert.isNotNull, true).to.not.equal(null);
    };

    /**
     * ### .isNaN
     *
     * Asserts that value is NaN.
     *
     *     assert.isNaN(NaN, 'NaN is NaN');
     *
     * @name isNaN
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isNaN = function (val, msg) {
      new Assertion(val, msg, assert.isNaN, true).to.be.NaN;
    };

    /**
     * ### .isNotNaN
     *
     * Asserts that value is not NaN.
     *
     *     assert.isNotNaN(4, '4 is not NaN');
     *
     * @name isNotNaN
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */
    assert.isNotNaN = function (val, msg) {
      new Assertion(val, msg, assert.isNotNaN, true).not.to.be.NaN;
    };

    /**
     * ### .exists
     *
     * Asserts that the target is neither `null` nor `undefined`.
     *
     *     var foo = 'hi';
     *
     *     assert.exists(foo, 'foo is neither `null` nor `undefined`');
     *
     * @name exists
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.exists = function (val, msg) {
      new Assertion(val, msg, assert.exists, true).to.exist;
    };

    /**
     * ### .notExists
     *
     * Asserts that the target is either `null` or `undefined`.
     *
     *     var bar = null
     *       , baz;
     *
     *     assert.notExists(bar);
     *     assert.notExists(baz, 'baz is either null or undefined');
     *
     * @name notExists
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notExists = function (val, msg) {
      new Assertion(val, msg, assert.notExists, true).to.not.exist;
    };

    /**
     * ### .isUndefined(value, [message])
     *
     * Asserts that `value` is `undefined`.
     *
     *     var tea;
     *     assert.isUndefined(tea, 'no tea defined');
     *
     * @name isUndefined
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isUndefined = function (val, msg) {
      new Assertion(val, msg, assert.isUndefined, true).to.equal(undefined);
    };

    /**
     * ### .isDefined(value, [message])
     *
     * Asserts that `value` is not `undefined`.
     *
     *     var tea = 'cup of chai';
     *     assert.isDefined(tea, 'tea has been defined');
     *
     * @name isDefined
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isDefined = function (val, msg) {
      new Assertion(val, msg, assert.isDefined, true).to.not.equal(undefined);
    };

    /**
     * ### .isFunction(value, [message])
     *
     * Asserts that `value` is a function.
     *
     *     function serveTea() { return 'cup of tea'; };
     *     assert.isFunction(serveTea, 'great, we can have tea now');
     *
     * @name isFunction
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isFunction = function (val, msg) {
      new Assertion(val, msg, assert.isFunction, true).to.be.a('function');
    };

    /**
     * ### .isNotFunction(value, [message])
     *
     * Asserts that `value` is _not_ a function.
     *
     *     var serveTea = [ 'heat', 'pour', 'sip' ];
     *     assert.isNotFunction(serveTea, 'great, we have listed the steps');
     *
     * @name isNotFunction
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isNotFunction = function (val, msg) {
      new Assertion(val, msg, assert.isNotFunction, true).to.not.be.a('function');
    };

    /**
     * ### .isObject(value, [message])
     *
     * Asserts that `value` is an object of type 'Object' (as revealed by `Object.prototype.toString`).
     * _The assertion does not match subclassed objects._
     *
     *     var selection = { name: 'Chai', serve: 'with spices' };
     *     assert.isObject(selection, 'tea selection is an object');
     *
     * @name isObject
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isObject = function (val, msg) {
      new Assertion(val, msg, assert.isObject, true).to.be.a('object');
    };

    /**
     * ### .isNotObject(value, [message])
     *
     * Asserts that `value` is _not_ an object of type 'Object' (as revealed by `Object.prototype.toString`).
     *
     *     var selection = 'chai'
     *     assert.isNotObject(selection, 'tea selection is not an object');
     *     assert.isNotObject(null, 'null is not an object');
     *
     * @name isNotObject
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isNotObject = function (val, msg) {
      new Assertion(val, msg, assert.isNotObject, true).to.not.be.a('object');
    };

    /**
     * ### .isArray(value, [message])
     *
     * Asserts that `value` is an array.
     *
     *     var menu = [ 'green', 'chai', 'oolong' ];
     *     assert.isArray(menu, 'what kind of tea do we want?');
     *
     * @name isArray
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isArray = function (val, msg) {
      new Assertion(val, msg, assert.isArray, true).to.be.an('array');
    };

    /**
     * ### .isNotArray(value, [message])
     *
     * Asserts that `value` is _not_ an array.
     *
     *     var menu = 'green|chai|oolong';
     *     assert.isNotArray(menu, 'what kind of tea do we want?');
     *
     * @name isNotArray
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isNotArray = function (val, msg) {
      new Assertion(val, msg, assert.isNotArray, true).to.not.be.an('array');
    };

    /**
     * ### .isString(value, [message])
     *
     * Asserts that `value` is a string.
     *
     *     var teaOrder = 'chai';
     *     assert.isString(teaOrder, 'order placed');
     *
     * @name isString
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isString = function (val, msg) {
      new Assertion(val, msg, assert.isString, true).to.be.a('string');
    };

    /**
     * ### .isNotString(value, [message])
     *
     * Asserts that `value` is _not_ a string.
     *
     *     var teaOrder = 4;
     *     assert.isNotString(teaOrder, 'order placed');
     *
     * @name isNotString
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isNotString = function (val, msg) {
      new Assertion(val, msg, assert.isNotString, true).to.not.be.a('string');
    };

    /**
     * ### .isNumber(value, [message])
     *
     * Asserts that `value` is a number.
     *
     *     var cups = 2;
     *     assert.isNumber(cups, 'how many cups');
     *
     * @name isNumber
     * @param {Number} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isNumber = function (val, msg) {
      new Assertion(val, msg, assert.isNumber, true).to.be.a('number');
    };

    /**
     * ### .isNotNumber(value, [message])
     *
     * Asserts that `value` is _not_ a number.
     *
     *     var cups = '2 cups please';
     *     assert.isNotNumber(cups, 'how many cups');
     *
     * @name isNotNumber
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isNotNumber = function (val, msg) {
      new Assertion(val, msg, assert.isNotNumber, true).to.not.be.a('number');
    };

     /**
     * ### .isFinite(value, [message])
     *
     * Asserts that `value` is a finite number. Unlike `.isNumber`, this will fail for `NaN` and `Infinity`.
     *
     *     var cups = 2;
     *     assert.isFinite(cups, 'how many cups');
     *
     *     assert.isFinite(NaN); // throws
     *
     * @name isFinite
     * @param {Number} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isFinite = function (val, msg) {
      new Assertion(val, msg, assert.isFinite, true).to.be.finite;
    };

    /**
     * ### .isBoolean(value, [message])
     *
     * Asserts that `value` is a boolean.
     *
     *     var teaReady = true
     *       , teaServed = false;
     *
     *     assert.isBoolean(teaReady, 'is the tea ready');
     *     assert.isBoolean(teaServed, 'has tea been served');
     *
     * @name isBoolean
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isBoolean = function (val, msg) {
      new Assertion(val, msg, assert.isBoolean, true).to.be.a('boolean');
    };

    /**
     * ### .isNotBoolean(value, [message])
     *
     * Asserts that `value` is _not_ a boolean.
     *
     *     var teaReady = 'yep'
     *       , teaServed = 'nope';
     *
     *     assert.isNotBoolean(teaReady, 'is the tea ready');
     *     assert.isNotBoolean(teaServed, 'has tea been served');
     *
     * @name isNotBoolean
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.isNotBoolean = function (val, msg) {
      new Assertion(val, msg, assert.isNotBoolean, true).to.not.be.a('boolean');
    };

    /**
     * ### .typeOf(value, name, [message])
     *
     * Asserts that `value`'s type is `name`, as determined by
     * `Object.prototype.toString`.
     *
     *     assert.typeOf({ tea: 'chai' }, 'object', 'we have an object');
     *     assert.typeOf(['chai', 'jasmine'], 'array', 'we have an array');
     *     assert.typeOf('tea', 'string', 'we have a string');
     *     assert.typeOf(/tea/, 'regexp', 'we have a regular expression');
     *     assert.typeOf(null, 'null', 'we have a null');
     *     assert.typeOf(undefined, 'undefined', 'we have an undefined');
     *
     * @name typeOf
     * @param {Mixed} value
     * @param {String} name
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.typeOf = function (val, type, msg) {
      new Assertion(val, msg, assert.typeOf, true).to.be.a(type);
    };

    /**
     * ### .notTypeOf(value, name, [message])
     *
     * Asserts that `value`'s type is _not_ `name`, as determined by
     * `Object.prototype.toString`.
     *
     *     assert.notTypeOf('tea', 'number', 'strings are not numbers');
     *
     * @name notTypeOf
     * @param {Mixed} value
     * @param {String} typeof name
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notTypeOf = function (val, type, msg) {
      new Assertion(val, msg, assert.notTypeOf, true).to.not.be.a(type);
    };

    /**
     * ### .instanceOf(object, constructor, [message])
     *
     * Asserts that `value` is an instance of `constructor`.
     *
     *     var Tea = function (name) { this.name = name; }
     *       , chai = new Tea('chai');
     *
     *     assert.instanceOf(chai, Tea, 'chai is an instance of tea');
     *
     * @name instanceOf
     * @param {Object} object
     * @param {Constructor} constructor
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.instanceOf = function (val, type, msg) {
      new Assertion(val, msg, assert.instanceOf, true).to.be.instanceOf(type);
    };

    /**
     * ### .notInstanceOf(object, constructor, [message])
     *
     * Asserts `value` is not an instance of `constructor`.
     *
     *     var Tea = function (name) { this.name = name; }
     *       , chai = new String('chai');
     *
     *     assert.notInstanceOf(chai, Tea, 'chai is not an instance of tea');
     *
     * @name notInstanceOf
     * @param {Object} object
     * @param {Constructor} constructor
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notInstanceOf = function (val, type, msg) {
      new Assertion(val, msg, assert.notInstanceOf, true)
        .to.not.be.instanceOf(type);
    };

    /**
     * ### .include(haystack, needle, [message])
     *
     * Asserts that `haystack` includes `needle`. Can be used to assert the
     * inclusion of a value in an array, a substring in a string, or a subset of
     * properties in an object.
     *
     *     assert.include([1,2,3], 2, 'array contains value');
     *     assert.include('foobar', 'foo', 'string contains substring');
     *     assert.include({ foo: 'bar', hello: 'universe' }, { foo: 'bar' }, 'object contains property');
     *
     * Strict equality (===) is used. When asserting the inclusion of a value in
     * an array, the array is searched for an element that's strictly equal to the
     * given value. When asserting a subset of properties in an object, the object
     * is searched for the given property keys, checking that each one is present
     * and stricty equal to the given property value. For instance:
     *
     *     var obj1 = {a: 1}
     *       , obj2 = {b: 2};
     *     assert.include([obj1, obj2], obj1);
     *     assert.include({foo: obj1, bar: obj2}, {foo: obj1});
     *     assert.include({foo: obj1, bar: obj2}, {foo: obj1, bar: obj2});
     *
     * @name include
     * @param {Array|String} haystack
     * @param {Mixed} needle
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.include = function (exp, inc, msg) {
      new Assertion(exp, msg, assert.include, true).include(inc);
    };

    /**
     * ### .notInclude(haystack, needle, [message])
     *
     * Asserts that `haystack` does not include `needle`. Can be used to assert
     * the absence of a value in an array, a substring in a string, or a subset of
     * properties in an object.
     *
     *     assert.notInclude([1,2,3], 4, 'array doesn't contain value');
     *     assert.notInclude('foobar', 'baz', 'string doesn't contain substring');
     *     assert.notInclude({ foo: 'bar', hello: 'universe' }, { foo: 'baz' }, 'object doesn't contain property');
     *
     * Strict equality (===) is used. When asserting the absence of a value in an
     * array, the array is searched to confirm the absence of an element that's
     * strictly equal to the given value. When asserting a subset of properties in
     * an object, the object is searched to confirm that at least one of the given
     * property keys is either not present or not strictly equal to the given
     * property value. For instance:
     *
     *     var obj1 = {a: 1}
     *       , obj2 = {b: 2};
     *     assert.notInclude([obj1, obj2], {a: 1});
     *     assert.notInclude({foo: obj1, bar: obj2}, {foo: {a: 1}});
     *     assert.notInclude({foo: obj1, bar: obj2}, {foo: obj1, bar: {b: 2}});
     *
     * @name notInclude
     * @param {Array|String} haystack
     * @param {Mixed} needle
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notInclude = function (exp, inc, msg) {
      new Assertion(exp, msg, assert.notInclude, true).not.include(inc);
    };

    /**
     * ### .deepInclude(haystack, needle, [message])
     *
     * Asserts that `haystack` includes `needle`. Can be used to assert the
     * inclusion of a value in an array or a subset of properties in an object.
     * Deep equality is used.
     *
     *     var obj1 = {a: 1}
     *       , obj2 = {b: 2};
     *     assert.deepInclude([obj1, obj2], {a: 1});
     *     assert.deepInclude({foo: obj1, bar: obj2}, {foo: {a: 1}});
     *     assert.deepInclude({foo: obj1, bar: obj2}, {foo: {a: 1}, bar: {b: 2}});
     *
     * @name deepInclude
     * @param {Array|String} haystack
     * @param {Mixed} needle
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.deepInclude = function (exp, inc, msg) {
      new Assertion(exp, msg, assert.deepInclude, true).deep.include(inc);
    };

    /**
     * ### .notDeepInclude(haystack, needle, [message])
     *
     * Asserts that `haystack` does not include `needle`. Can be used to assert
     * the absence of a value in an array or a subset of properties in an object.
     * Deep equality is used.
     *
     *     var obj1 = {a: 1}
     *       , obj2 = {b: 2};
     *     assert.notDeepInclude([obj1, obj2], {a: 9});
     *     assert.notDeepInclude({foo: obj1, bar: obj2}, {foo: {a: 9}});
     *     assert.notDeepInclude({foo: obj1, bar: obj2}, {foo: {a: 1}, bar: {b: 9}});
     *
     * @name notDeepInclude
     * @param {Array|String} haystack
     * @param {Mixed} needle
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notDeepInclude = function (exp, inc, msg) {
      new Assertion(exp, msg, assert.notDeepInclude, true).not.deep.include(inc);
    };

    /**
     * ### .nestedInclude(haystack, needle, [message])
     *
     * Asserts that 'haystack' includes 'needle'.
     * Can be used to assert the inclusion of a subset of properties in an
     * object.
     * Enables the use of dot- and bracket-notation for referencing nested
     * properties.
     * '[]' and '.' in property names can be escaped using double backslashes.
     *
     *     assert.nestedInclude({'.a': {'b': 'x'}}, {'\\.a.[b]': 'x'});
     *     assert.nestedInclude({'a': {'[b]': 'x'}}, {'a.\\[b\\]': 'x'});
     *
     * @name nestedInclude
     * @param {Object} haystack
     * @param {Object} needle
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.nestedInclude = function (exp, inc, msg) {
      new Assertion(exp, msg, assert.nestedInclude, true).nested.include(inc);
    };

    /**
     * ### .notNestedInclude(haystack, needle, [message])
     *
     * Asserts that 'haystack' does not include 'needle'.
     * Can be used to assert the absence of a subset of properties in an
     * object.
     * Enables the use of dot- and bracket-notation for referencing nested
     * properties.
     * '[]' and '.' in property names can be escaped using double backslashes.
     *
     *     assert.notNestedInclude({'.a': {'b': 'x'}}, {'\\.a.b': 'y'});
     *     assert.notNestedInclude({'a': {'[b]': 'x'}}, {'a.\\[b\\]': 'y'});
     *
     * @name notNestedInclude
     * @param {Object} haystack
     * @param {Object} needle
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notNestedInclude = function (exp, inc, msg) {
      new Assertion(exp, msg, assert.notNestedInclude, true)
        .not.nested.include(inc);
    };

    /**
     * ### .deepNestedInclude(haystack, needle, [message])
     *
     * Asserts that 'haystack' includes 'needle'.
     * Can be used to assert the inclusion of a subset of properties in an
     * object while checking for deep equality.
     * Enables the use of dot- and bracket-notation for referencing nested
     * properties.
     * '[]' and '.' in property names can be escaped using double backslashes.
     *
     *     assert.deepNestedInclude({a: {b: [{x: 1}]}}, {'a.b[0]': {x: 1}});
     *     assert.deepNestedInclude({'.a': {'[b]': {x: 1}}}, {'\\.a.\\[b\\]': {x: 1}});
     *
     * @name deepNestedInclude
     * @param {Object} haystack
     * @param {Object} needle
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.deepNestedInclude = function(exp, inc, msg) {
      new Assertion(exp, msg, assert.deepNestedInclude, true)
        .deep.nested.include(inc);
    };

    /**
     * ### .notDeepNestedInclude(haystack, needle, [message])
     *
     * Asserts that 'haystack' does not include 'needle'.
     * Can be used to assert the absence of a subset of properties in an
     * object while checking for deep equality.
     * Enables the use of dot- and bracket-notation for referencing nested
     * properties.
     * '[]' and '.' in property names can be escaped using double backslashes.
     *
     *     assert.notDeepNestedInclude({a: {b: [{x: 1}]}}, {'a.b[0]': {y: 1}})
     *     assert.notDeepNestedInclude({'.a': {'[b]': {x: 1}}}, {'\\.a.\\[b\\]': {y: 2}});
     *
     * @name notDeepNestedInclude
     * @param {Object} haystack
     * @param {Object} needle
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notDeepNestedInclude = function(exp, inc, msg) {
      new Assertion(exp, msg, assert.notDeepNestedInclude, true)
        .not.deep.nested.include(inc);
    };

    /**
     * ### .ownInclude(haystack, needle, [message])
     *
     * Asserts that 'haystack' includes 'needle'.
     * Can be used to assert the inclusion of a subset of properties in an
     * object while ignoring inherited properties.
     *
     *     assert.ownInclude({ a: 1 }, { a: 1 });
     *
     * @name ownInclude
     * @param {Object} haystack
     * @param {Object} needle
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.ownInclude = function(exp, inc, msg) {
      new Assertion(exp, msg, assert.ownInclude, true).own.include(inc);
    };

    /**
     * ### .notOwnInclude(haystack, needle, [message])
     *
     * Asserts that 'haystack' includes 'needle'.
     * Can be used to assert the absence of a subset of properties in an
     * object while ignoring inherited properties.
     *
     *     Object.prototype.b = 2;
     *
     *     assert.notOwnInclude({ a: 1 }, { b: 2 });
     *
     * @name notOwnInclude
     * @param {Object} haystack
     * @param {Object} needle
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notOwnInclude = function(exp, inc, msg) {
      new Assertion(exp, msg, assert.notOwnInclude, true).not.own.include(inc);
    };

    /**
     * ### .deepOwnInclude(haystack, needle, [message])
     *
     * Asserts that 'haystack' includes 'needle'.
     * Can be used to assert the inclusion of a subset of properties in an
     * object while ignoring inherited properties and checking for deep equality.
     *
     *      assert.deepOwnInclude({a: {b: 2}}, {a: {b: 2}});
     *
     * @name deepOwnInclude
     * @param {Object} haystack
     * @param {Object} needle
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.deepOwnInclude = function(exp, inc, msg) {
      new Assertion(exp, msg, assert.deepOwnInclude, true)
        .deep.own.include(inc);
    };

     /**
     * ### .notDeepOwnInclude(haystack, needle, [message])
     *
     * Asserts that 'haystack' includes 'needle'.
     * Can be used to assert the absence of a subset of properties in an
     * object while ignoring inherited properties and checking for deep equality.
     *
     *      assert.notDeepOwnInclude({a: {b: 2}}, {a: {c: 3}});
     *
     * @name notDeepOwnInclude
     * @param {Object} haystack
     * @param {Object} needle
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notDeepOwnInclude = function(exp, inc, msg) {
      new Assertion(exp, msg, assert.notDeepOwnInclude, true)
        .not.deep.own.include(inc);
    };

    /**
     * ### .match(value, regexp, [message])
     *
     * Asserts that `value` matches the regular expression `regexp`.
     *
     *     assert.match('foobar', /^foo/, 'regexp matches');
     *
     * @name match
     * @param {Mixed} value
     * @param {RegExp} regexp
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.match = function (exp, re, msg) {
      new Assertion(exp, msg, assert.match, true).to.match(re);
    };

    /**
     * ### .notMatch(value, regexp, [message])
     *
     * Asserts that `value` does not match the regular expression `regexp`.
     *
     *     assert.notMatch('foobar', /^foo/, 'regexp does not match');
     *
     * @name notMatch
     * @param {Mixed} value
     * @param {RegExp} regexp
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notMatch = function (exp, re, msg) {
      new Assertion(exp, msg, assert.notMatch, true).to.not.match(re);
    };

    /**
     * ### .property(object, property, [message])
     *
     * Asserts that `object` has a direct or inherited property named by
     * `property`.
     *
     *     assert.property({ tea: { green: 'matcha' }}, 'tea');
     *     assert.property({ tea: { green: 'matcha' }}, 'toString');
     *
     * @name property
     * @param {Object} object
     * @param {String} property
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.property = function (obj, prop, msg) {
      new Assertion(obj, msg, assert.property, true).to.have.property(prop);
    };

    /**
     * ### .notProperty(object, property, [message])
     *
     * Asserts that `object` does _not_ have a direct or inherited property named
     * by `property`.
     *
     *     assert.notProperty({ tea: { green: 'matcha' }}, 'coffee');
     *
     * @name notProperty
     * @param {Object} object
     * @param {String} property
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notProperty = function (obj, prop, msg) {
      new Assertion(obj, msg, assert.notProperty, true)
        .to.not.have.property(prop);
    };

    /**
     * ### .propertyVal(object, property, value, [message])
     *
     * Asserts that `object` has a direct or inherited property named by
     * `property` with a value given by `value`. Uses a strict equality check
     * (===).
     *
     *     assert.propertyVal({ tea: 'is good' }, 'tea', 'is good');
     *
     * @name propertyVal
     * @param {Object} object
     * @param {String} property
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.propertyVal = function (obj, prop, val, msg) {
      new Assertion(obj, msg, assert.propertyVal, true)
        .to.have.property(prop, val);
    };

    /**
     * ### .notPropertyVal(object, property, value, [message])
     *
     * Asserts that `object` does _not_ have a direct or inherited property named
     * by `property` with value given by `value`. Uses a strict equality check
     * (===).
     *
     *     assert.notPropertyVal({ tea: 'is good' }, 'tea', 'is bad');
     *     assert.notPropertyVal({ tea: 'is good' }, 'coffee', 'is good');
     *
     * @name notPropertyVal
     * @param {Object} object
     * @param {String} property
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notPropertyVal = function (obj, prop, val, msg) {
      new Assertion(obj, msg, assert.notPropertyVal, true)
        .to.not.have.property(prop, val);
    };

    /**
     * ### .deepPropertyVal(object, property, value, [message])
     *
     * Asserts that `object` has a direct or inherited property named by
     * `property` with a value given by `value`. Uses a deep equality check.
     *
     *     assert.deepPropertyVal({ tea: { green: 'matcha' } }, 'tea', { green: 'matcha' });
     *
     * @name deepPropertyVal
     * @param {Object} object
     * @param {String} property
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.deepPropertyVal = function (obj, prop, val, msg) {
      new Assertion(obj, msg, assert.deepPropertyVal, true)
        .to.have.deep.property(prop, val);
    };

    /**
     * ### .notDeepPropertyVal(object, property, value, [message])
     *
     * Asserts that `object` does _not_ have a direct or inherited property named
     * by `property` with value given by `value`. Uses a deep equality check.
     *
     *     assert.notDeepPropertyVal({ tea: { green: 'matcha' } }, 'tea', { black: 'matcha' });
     *     assert.notDeepPropertyVal({ tea: { green: 'matcha' } }, 'tea', { green: 'oolong' });
     *     assert.notDeepPropertyVal({ tea: { green: 'matcha' } }, 'coffee', { green: 'matcha' });
     *
     * @name notDeepPropertyVal
     * @param {Object} object
     * @param {String} property
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notDeepPropertyVal = function (obj, prop, val, msg) {
      new Assertion(obj, msg, assert.notDeepPropertyVal, true)
        .to.not.have.deep.property(prop, val);
    };

    /**
     * ### .ownProperty(object, property, [message])
     *
     * Asserts that `object` has a direct property named by `property`. Inherited
     * properties aren't checked.
     *
     *     assert.ownProperty({ tea: { green: 'matcha' }}, 'tea');
     *
     * @name ownProperty
     * @param {Object} object
     * @param {String} property
     * @param {String} message
     * @api public
     */

    assert.ownProperty = function (obj, prop, msg) {
      new Assertion(obj, msg, assert.ownProperty, true)
        .to.have.own.property(prop);
    };

    /**
     * ### .notOwnProperty(object, property, [message])
     *
     * Asserts that `object` does _not_ have a direct property named by
     * `property`. Inherited properties aren't checked.
     *
     *     assert.notOwnProperty({ tea: { green: 'matcha' }}, 'coffee');
     *     assert.notOwnProperty({}, 'toString');
     *
     * @name notOwnProperty
     * @param {Object} object
     * @param {String} property
     * @param {String} message
     * @api public
     */

    assert.notOwnProperty = function (obj, prop, msg) {
      new Assertion(obj, msg, assert.notOwnProperty, true)
        .to.not.have.own.property(prop);
    };

    /**
     * ### .ownPropertyVal(object, property, value, [message])
     *
     * Asserts that `object` has a direct property named by `property` and a value
     * equal to the provided `value`. Uses a strict equality check (===).
     * Inherited properties aren't checked.
     *
     *     assert.ownPropertyVal({ coffee: 'is good'}, 'coffee', 'is good');
     *
     * @name ownPropertyVal
     * @param {Object} object
     * @param {String} property
     * @param {Mixed} value
     * @param {String} message
     * @api public
     */

    assert.ownPropertyVal = function (obj, prop, value, msg) {
      new Assertion(obj, msg, assert.ownPropertyVal, true)
        .to.have.own.property(prop, value);
    };

    /**
     * ### .notOwnPropertyVal(object, property, value, [message])
     *
     * Asserts that `object` does _not_ have a direct property named by `property`
     * with a value equal to the provided `value`. Uses a strict equality check
     * (===). Inherited properties aren't checked.
     *
     *     assert.notOwnPropertyVal({ tea: 'is better'}, 'tea', 'is worse');
     *     assert.notOwnPropertyVal({}, 'toString', Object.prototype.toString);
     *
     * @name notOwnPropertyVal
     * @param {Object} object
     * @param {String} property
     * @param {Mixed} value
     * @param {String} message
     * @api public
     */

    assert.notOwnPropertyVal = function (obj, prop, value, msg) {
      new Assertion(obj, msg, assert.notOwnPropertyVal, true)
        .to.not.have.own.property(prop, value);
    };

    /**
     * ### .deepOwnPropertyVal(object, property, value, [message])
     *
     * Asserts that `object` has a direct property named by `property` and a value
     * equal to the provided `value`. Uses a deep equality check. Inherited
     * properties aren't checked.
     *
     *     assert.deepOwnPropertyVal({ tea: { green: 'matcha' } }, 'tea', { green: 'matcha' });
     *
     * @name deepOwnPropertyVal
     * @param {Object} object
     * @param {String} property
     * @param {Mixed} value
     * @param {String} message
     * @api public
     */

    assert.deepOwnPropertyVal = function (obj, prop, value, msg) {
      new Assertion(obj, msg, assert.deepOwnPropertyVal, true)
        .to.have.deep.own.property(prop, value);
    };

    /**
     * ### .notDeepOwnPropertyVal(object, property, value, [message])
     *
     * Asserts that `object` does _not_ have a direct property named by `property`
     * with a value equal to the provided `value`. Uses a deep equality check.
     * Inherited properties aren't checked.
     *
     *     assert.notDeepOwnPropertyVal({ tea: { green: 'matcha' } }, 'tea', { black: 'matcha' });
     *     assert.notDeepOwnPropertyVal({ tea: { green: 'matcha' } }, 'tea', { green: 'oolong' });
     *     assert.notDeepOwnPropertyVal({ tea: { green: 'matcha' } }, 'coffee', { green: 'matcha' });
     *     assert.notDeepOwnPropertyVal({}, 'toString', Object.prototype.toString);
     *
     * @name notDeepOwnPropertyVal
     * @param {Object} object
     * @param {String} property
     * @param {Mixed} value
     * @param {String} message
     * @api public
     */

    assert.notDeepOwnPropertyVal = function (obj, prop, value, msg) {
      new Assertion(obj, msg, assert.notDeepOwnPropertyVal, true)
        .to.not.have.deep.own.property(prop, value);
    };

    /**
     * ### .nestedProperty(object, property, [message])
     *
     * Asserts that `object` has a direct or inherited property named by
     * `property`, which can be a string using dot- and bracket-notation for
     * nested reference.
     *
     *     assert.nestedProperty({ tea: { green: 'matcha' }}, 'tea.green');
     *
     * @name nestedProperty
     * @param {Object} object
     * @param {String} property
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.nestedProperty = function (obj, prop, msg) {
      new Assertion(obj, msg, assert.nestedProperty, true)
        .to.have.nested.property(prop);
    };

    /**
     * ### .notNestedProperty(object, property, [message])
     *
     * Asserts that `object` does _not_ have a property named by `property`, which
     * can be a string using dot- and bracket-notation for nested reference. The
     * property cannot exist on the object nor anywhere in its prototype chain.
     *
     *     assert.notNestedProperty({ tea: { green: 'matcha' }}, 'tea.oolong');
     *
     * @name notNestedProperty
     * @param {Object} object
     * @param {String} property
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notNestedProperty = function (obj, prop, msg) {
      new Assertion(obj, msg, assert.notNestedProperty, true)
        .to.not.have.nested.property(prop);
    };

    /**
     * ### .nestedPropertyVal(object, property, value, [message])
     *
     * Asserts that `object` has a property named by `property` with value given
     * by `value`. `property` can use dot- and bracket-notation for nested
     * reference. Uses a strict equality check (===).
     *
     *     assert.nestedPropertyVal({ tea: { green: 'matcha' }}, 'tea.green', 'matcha');
     *
     * @name nestedPropertyVal
     * @param {Object} object
     * @param {String} property
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.nestedPropertyVal = function (obj, prop, val, msg) {
      new Assertion(obj, msg, assert.nestedPropertyVal, true)
        .to.have.nested.property(prop, val);
    };

    /**
     * ### .notNestedPropertyVal(object, property, value, [message])
     *
     * Asserts that `object` does _not_ have a property named by `property` with
     * value given by `value`. `property` can use dot- and bracket-notation for
     * nested reference. Uses a strict equality check (===).
     *
     *     assert.notNestedPropertyVal({ tea: { green: 'matcha' }}, 'tea.green', 'konacha');
     *     assert.notNestedPropertyVal({ tea: { green: 'matcha' }}, 'coffee.green', 'matcha');
     *
     * @name notNestedPropertyVal
     * @param {Object} object
     * @param {String} property
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notNestedPropertyVal = function (obj, prop, val, msg) {
      new Assertion(obj, msg, assert.notNestedPropertyVal, true)
        .to.not.have.nested.property(prop, val);
    };

    /**
     * ### .deepNestedPropertyVal(object, property, value, [message])
     *
     * Asserts that `object` has a property named by `property` with a value given
     * by `value`. `property` can use dot- and bracket-notation for nested
     * reference. Uses a deep equality check.
     *
     *     assert.deepNestedPropertyVal({ tea: { green: { matcha: 'yum' } } }, 'tea.green', { matcha: 'yum' });
     *
     * @name deepNestedPropertyVal
     * @param {Object} object
     * @param {String} property
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.deepNestedPropertyVal = function (obj, prop, val, msg) {
      new Assertion(obj, msg, assert.deepNestedPropertyVal, true)
        .to.have.deep.nested.property(prop, val);
    };

    /**
     * ### .notDeepNestedPropertyVal(object, property, value, [message])
     *
     * Asserts that `object` does _not_ have a property named by `property` with
     * value given by `value`. `property` can use dot- and bracket-notation for
     * nested reference. Uses a deep equality check.
     *
     *     assert.notDeepNestedPropertyVal({ tea: { green: { matcha: 'yum' } } }, 'tea.green', { oolong: 'yum' });
     *     assert.notDeepNestedPropertyVal({ tea: { green: { matcha: 'yum' } } }, 'tea.green', { matcha: 'yuck' });
     *     assert.notDeepNestedPropertyVal({ tea: { green: { matcha: 'yum' } } }, 'tea.black', { matcha: 'yum' });
     *
     * @name notDeepNestedPropertyVal
     * @param {Object} object
     * @param {String} property
     * @param {Mixed} value
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notDeepNestedPropertyVal = function (obj, prop, val, msg) {
      new Assertion(obj, msg, assert.notDeepNestedPropertyVal, true)
        .to.not.have.deep.nested.property(prop, val);
    }

    /**
     * ### .lengthOf(object, length, [message])
     *
     * Asserts that `object` has a `length` property with the expected value.
     *
     *     assert.lengthOf([1,2,3], 3, 'array has length of 3');
     *     assert.lengthOf('foobar', 6, 'string has length of 6');
     *
     * @name lengthOf
     * @param {Mixed} object
     * @param {Number} length
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.lengthOf = function (exp, len, msg) {
      new Assertion(exp, msg, assert.lengthOf, true).to.have.lengthOf(len);
    };

    /**
     * ### .hasAnyKeys(object, [keys], [message])
     *
     * Asserts that `object` has at least one of the `keys` provided.
     * You can also provide a single object instead of a `keys` array and its keys
     * will be used as the expected set of keys.
     *
     *     assert.hasAnyKeys({foo: 1, bar: 2, baz: 3}, ['foo', 'iDontExist', 'baz']);
     *     assert.hasAnyKeys({foo: 1, bar: 2, baz: 3}, {foo: 30, iDontExist: 99, baz: 1337});
     *     assert.hasAnyKeys(new Map([[{foo: 1}, 'bar'], ['key', 'value']]), [{foo: 1}, 'key']);
     *     assert.hasAnyKeys(new Set([{foo: 'bar'}, 'anotherKey']), [{foo: 'bar'}, 'anotherKey']);
     *
     * @name hasAnyKeys
     * @param {Mixed} object
     * @param {Array|Object} keys
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.hasAnyKeys = function (obj, keys, msg) {
      new Assertion(obj, msg, assert.hasAnyKeys, true).to.have.any.keys(keys);
    }

    /**
     * ### .hasAllKeys(object, [keys], [message])
     *
     * Asserts that `object` has all and only all of the `keys` provided.
     * You can also provide a single object instead of a `keys` array and its keys
     * will be used as the expected set of keys.
     *
     *     assert.hasAllKeys({foo: 1, bar: 2, baz: 3}, ['foo', 'bar', 'baz']);
     *     assert.hasAllKeys({foo: 1, bar: 2, baz: 3}, {foo: 30, bar: 99, baz: 1337]);
     *     assert.hasAllKeys(new Map([[{foo: 1}, 'bar'], ['key', 'value']]), [{foo: 1}, 'key']);
     *     assert.hasAllKeys(new Set([{foo: 'bar'}, 'anotherKey'], [{foo: 'bar'}, 'anotherKey']);
     *
     * @name hasAllKeys
     * @param {Mixed} object
     * @param {String[]} keys
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.hasAllKeys = function (obj, keys, msg) {
      new Assertion(obj, msg, assert.hasAllKeys, true).to.have.all.keys(keys);
    }

    /**
     * ### .containsAllKeys(object, [keys], [message])
     *
     * Asserts that `object` has all of the `keys` provided but may have more keys not listed.
     * You can also provide a single object instead of a `keys` array and its keys
     * will be used as the expected set of keys.
     *
     *     assert.containsAllKeys({foo: 1, bar: 2, baz: 3}, ['foo', 'baz']);
     *     assert.containsAllKeys({foo: 1, bar: 2, baz: 3}, ['foo', 'bar', 'baz']);
     *     assert.containsAllKeys({foo: 1, bar: 2, baz: 3}, {foo: 30, baz: 1337});
     *     assert.containsAllKeys({foo: 1, bar: 2, baz: 3}, {foo: 30, bar: 99, baz: 1337});
     *     assert.containsAllKeys(new Map([[{foo: 1}, 'bar'], ['key', 'value']]), [{foo: 1}]);
     *     assert.containsAllKeys(new Map([[{foo: 1}, 'bar'], ['key', 'value']]), [{foo: 1}, 'key']);
     *     assert.containsAllKeys(new Set([{foo: 'bar'}, 'anotherKey'], [{foo: 'bar'}]);
     *     assert.containsAllKeys(new Set([{foo: 'bar'}, 'anotherKey'], [{foo: 'bar'}, 'anotherKey']);
     *
     * @name containsAllKeys
     * @param {Mixed} object
     * @param {String[]} keys
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.containsAllKeys = function (obj, keys, msg) {
      new Assertion(obj, msg, assert.containsAllKeys, true)
        .to.contain.all.keys(keys);
    }

    /**
     * ### .doesNotHaveAnyKeys(object, [keys], [message])
     *
     * Asserts that `object` has none of the `keys` provided.
     * You can also provide a single object instead of a `keys` array and its keys
     * will be used as the expected set of keys.
     *
     *     assert.doesNotHaveAnyKeys({foo: 1, bar: 2, baz: 3}, ['one', 'two', 'example']);
     *     assert.doesNotHaveAnyKeys({foo: 1, bar: 2, baz: 3}, {one: 1, two: 2, example: 'foo'});
     *     assert.doesNotHaveAnyKeys(new Map([[{foo: 1}, 'bar'], ['key', 'value']]), [{one: 'two'}, 'example']);
     *     assert.doesNotHaveAnyKeys(new Set([{foo: 'bar'}, 'anotherKey'], [{one: 'two'}, 'example']);
     *
     * @name doesNotHaveAnyKeys
     * @param {Mixed} object
     * @param {String[]} keys
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.doesNotHaveAnyKeys = function (obj, keys, msg) {
      new Assertion(obj, msg, assert.doesNotHaveAnyKeys, true)
        .to.not.have.any.keys(keys);
    }

    /**
     * ### .doesNotHaveAllKeys(object, [keys], [message])
     *
     * Asserts that `object` does not have at least one of the `keys` provided.
     * You can also provide a single object instead of a `keys` array and its keys
     * will be used as the expected set of keys.
     *
     *     assert.doesNotHaveAllKeys({foo: 1, bar: 2, baz: 3}, ['one', 'two', 'example']);
     *     assert.doesNotHaveAllKeys({foo: 1, bar: 2, baz: 3}, {one: 1, two: 2, example: 'foo'});
     *     assert.doesNotHaveAllKeys(new Map([[{foo: 1}, 'bar'], ['key', 'value']]), [{one: 'two'}, 'example']);
     *     assert.doesNotHaveAllKeys(new Set([{foo: 'bar'}, 'anotherKey'], [{one: 'two'}, 'example']);
     *
     * @name doesNotHaveAllKeys
     * @param {Mixed} object
     * @param {String[]} keys
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.doesNotHaveAllKeys = function (obj, keys, msg) {
      new Assertion(obj, msg, assert.doesNotHaveAllKeys, true)
        .to.not.have.all.keys(keys);
    }

    /**
     * ### .hasAnyDeepKeys(object, [keys], [message])
     *
     * Asserts that `object` has at least one of the `keys` provided.
     * Since Sets and Maps can have objects as keys you can use this assertion to perform
     * a deep comparison.
     * You can also provide a single object instead of a `keys` array and its keys
     * will be used as the expected set of keys.
     *
     *     assert.hasAnyDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [1, 2]]), {one: 'one'});
     *     assert.hasAnyDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [1, 2]]), [{one: 'one'}, {two: 'two'}]);
     *     assert.hasAnyDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [{two: 'two'}, 'valueTwo']]), [{one: 'one'}, {two: 'two'}]);
     *     assert.hasAnyDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), {one: 'one'});
     *     assert.hasAnyDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), [{one: 'one'}, {three: 'three'}]);
     *     assert.hasAnyDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), [{one: 'one'}, {two: 'two'}]);
     *
     * @name doesNotHaveAllKeys
     * @param {Mixed} object
     * @param {Array|Object} keys
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.hasAnyDeepKeys = function (obj, keys, msg) {
      new Assertion(obj, msg, assert.hasAnyDeepKeys, true)
        .to.have.any.deep.keys(keys);
    }

   /**
     * ### .hasAllDeepKeys(object, [keys], [message])
     *
     * Asserts that `object` has all and only all of the `keys` provided.
     * Since Sets and Maps can have objects as keys you can use this assertion to perform
     * a deep comparison.
     * You can also provide a single object instead of a `keys` array and its keys
     * will be used as the expected set of keys.
     *
     *     assert.hasAllDeepKeys(new Map([[{one: 'one'}, 'valueOne']]), {one: 'one'});
     *     assert.hasAllDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [{two: 'two'}, 'valueTwo']]), [{one: 'one'}, {two: 'two'}]);
     *     assert.hasAllDeepKeys(new Set([{one: 'one'}]), {one: 'one'});
     *     assert.hasAllDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), [{one: 'one'}, {two: 'two'}]);
     *
     * @name hasAllDeepKeys
     * @param {Mixed} object
     * @param {Array|Object} keys
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.hasAllDeepKeys = function (obj, keys, msg) {
      new Assertion(obj, msg, assert.hasAllDeepKeys, true)
        .to.have.all.deep.keys(keys);
    }

   /**
     * ### .containsAllDeepKeys(object, [keys], [message])
     *
     * Asserts that `object` contains all of the `keys` provided.
     * Since Sets and Maps can have objects as keys you can use this assertion to perform
     * a deep comparison.
     * You can also provide a single object instead of a `keys` array and its keys
     * will be used as the expected set of keys.
     *
     *     assert.containsAllDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [1, 2]]), {one: 'one'});
     *     assert.containsAllDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [{two: 'two'}, 'valueTwo']]), [{one: 'one'}, {two: 'two'}]);
     *     assert.containsAllDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), {one: 'one'});
     *     assert.containsAllDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), [{one: 'one'}, {two: 'two'}]);
     *
     * @name containsAllDeepKeys
     * @param {Mixed} object
     * @param {Array|Object} keys
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.containsAllDeepKeys = function (obj, keys, msg) {
      new Assertion(obj, msg, assert.containsAllDeepKeys, true)
        .to.contain.all.deep.keys(keys);
    }

   /**
     * ### .doesNotHaveAnyDeepKeys(object, [keys], [message])
     *
     * Asserts that `object` has none of the `keys` provided.
     * Since Sets and Maps can have objects as keys you can use this assertion to perform
     * a deep comparison.
     * You can also provide a single object instead of a `keys` array and its keys
     * will be used as the expected set of keys.
     *
     *     assert.doesNotHaveAnyDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [1, 2]]), {thisDoesNot: 'exist'});
     *     assert.doesNotHaveAnyDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [{two: 'two'}, 'valueTwo']]), [{twenty: 'twenty'}, {fifty: 'fifty'}]);
     *     assert.doesNotHaveAnyDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), {twenty: 'twenty'});
     *     assert.doesNotHaveAnyDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), [{twenty: 'twenty'}, {fifty: 'fifty'}]);
     *
     * @name doesNotHaveAnyDeepKeys
     * @param {Mixed} object
     * @param {Array|Object} keys
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.doesNotHaveAnyDeepKeys = function (obj, keys, msg) {
      new Assertion(obj, msg, assert.doesNotHaveAnyDeepKeys, true)
        .to.not.have.any.deep.keys(keys);
    }

   /**
     * ### .doesNotHaveAllDeepKeys(object, [keys], [message])
     *
     * Asserts that `object` does not have at least one of the `keys` provided.
     * Since Sets and Maps can have objects as keys you can use this assertion to perform
     * a deep comparison.
     * You can also provide a single object instead of a `keys` array and its keys
     * will be used as the expected set of keys.
     *
     *     assert.doesNotHaveAllDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [1, 2]]), {thisDoesNot: 'exist'});
     *     assert.doesNotHaveAllDeepKeys(new Map([[{one: 'one'}, 'valueOne'], [{two: 'two'}, 'valueTwo']]), [{twenty: 'twenty'}, {one: 'one'}]);
     *     assert.doesNotHaveAllDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), {twenty: 'twenty'});
     *     assert.doesNotHaveAllDeepKeys(new Set([{one: 'one'}, {two: 'two'}]), [{one: 'one'}, {fifty: 'fifty'}]);
     *
     * @name doesNotHaveAllDeepKeys
     * @param {Mixed} object
     * @param {Array|Object} keys
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.doesNotHaveAllDeepKeys = function (obj, keys, msg) {
      new Assertion(obj, msg, assert.doesNotHaveAllDeepKeys, true)
        .to.not.have.all.deep.keys(keys);
    }

   /**
     * ### .throws(fn, [errorLike/string/regexp], [string/regexp], [message])
     *
     * If `errorLike` is an `Error` constructor, asserts that `fn` will throw an error that is an
     * instance of `errorLike`.
     * If `errorLike` is an `Error` instance, asserts that the error thrown is the same
     * instance as `errorLike`.
     * If `errMsgMatcher` is provided, it also asserts that the error thrown will have a
     * message matching `errMsgMatcher`.
     *
     *     assert.throws(fn, 'function throws a reference error');
     *     assert.throws(fn, /function throws a reference error/);
     *     assert.throws(fn, ReferenceError);
     *     assert.throws(fn, errorInstance);
     *     assert.throws(fn, ReferenceError, 'Error thrown must be a ReferenceError and have this msg');
     *     assert.throws(fn, errorInstance, 'Error thrown must be the same errorInstance and have this msg');
     *     assert.throws(fn, ReferenceError, /Error thrown must be a ReferenceError and match this/);
     *     assert.throws(fn, errorInstance, /Error thrown must be the same errorInstance and match this/);
     *
     * @name throws
     * @alias throw
     * @alias Throw
     * @param {Function} fn
     * @param {ErrorConstructor|Error} errorLike
     * @param {RegExp|String} errMsgMatcher
     * @param {String} message
     * @see https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Error#Error_types
     * @namespace Assert
     * @api public
     */

    assert.throws = function (fn, errorLike, errMsgMatcher, msg) {
      if ('string' === typeof errorLike || errorLike instanceof RegExp) {
        errMsgMatcher = errorLike;
        errorLike = null;
      }

      var assertErr = new Assertion(fn, msg, assert.throws, true)
        .to.throw(errorLike, errMsgMatcher);
      return flag(assertErr, 'object');
    };

    /**
     * ### .doesNotThrow(fn, [errorLike/string/regexp], [string/regexp], [message])
     *
     * If `errorLike` is an `Error` constructor, asserts that `fn` will _not_ throw an error that is an
     * instance of `errorLike`.
     * If `errorLike` is an `Error` instance, asserts that the error thrown is _not_ the same
     * instance as `errorLike`.
     * If `errMsgMatcher` is provided, it also asserts that the error thrown will _not_ have a
     * message matching `errMsgMatcher`.
     *
     *     assert.doesNotThrow(fn, 'Any Error thrown must not have this message');
     *     assert.doesNotThrow(fn, /Any Error thrown must not match this/);
     *     assert.doesNotThrow(fn, Error);
     *     assert.doesNotThrow(fn, errorInstance);
     *     assert.doesNotThrow(fn, Error, 'Error must not have this message');
     *     assert.doesNotThrow(fn, errorInstance, 'Error must not have this message');
     *     assert.doesNotThrow(fn, Error, /Error must not match this/);
     *     assert.doesNotThrow(fn, errorInstance, /Error must not match this/);
     *
     * @name doesNotThrow
     * @param {Function} fn
     * @param {ErrorConstructor} errorLike
     * @param {RegExp|String} errMsgMatcher
     * @param {String} message
     * @see https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Error#Error_types
     * @namespace Assert
     * @api public
     */

    assert.doesNotThrow = function (fn, errorLike, errMsgMatcher, msg) {
      if ('string' === typeof errorLike || errorLike instanceof RegExp) {
        errMsgMatcher = errorLike;
        errorLike = null;
      }

      new Assertion(fn, msg, assert.doesNotThrow, true)
        .to.not.throw(errorLike, errMsgMatcher);
    };

    /**
     * ### .operator(val1, operator, val2, [message])
     *
     * Compares two values using `operator`.
     *
     *     assert.operator(1, '<', 2, 'everything is ok');
     *     assert.operator(1, '>', 2, 'this will fail');
     *
     * @name operator
     * @param {Mixed} val1
     * @param {String} operator
     * @param {Mixed} val2
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.operator = function (val, operator, val2, msg) {
      var ok;
      switch(operator) {
        case '==':
          ok = val == val2;
          break;
        case '===':
          ok = val === val2;
          break;
        case '>':
          ok = val > val2;
          break;
        case '>=':
          ok = val >= val2;
          break;
        case '<':
          ok = val < val2;
          break;
        case '<=':
          ok = val <= val2;
          break;
        case '!=':
          ok = val != val2;
          break;
        case '!==':
          ok = val !== val2;
          break;
        default:
          msg = msg ? msg + ': ' : msg;
          throw new chai.AssertionError(
            msg + 'Invalid operator "' + operator + '"',
            undefined,
            assert.operator
          );
      }
      var test = new Assertion(ok, msg, assert.operator, true);
      test.assert(
          true === flag(test, 'object')
        , 'expected ' + util.inspect(val) + ' to be ' + operator + ' ' + util.inspect(val2)
        , 'expected ' + util.inspect(val) + ' to not be ' + operator + ' ' + util.inspect(val2) );
    };

    /**
     * ### .closeTo(actual, expected, delta, [message])
     *
     * Asserts that the target is equal `expected`, to within a +/- `delta` range.
     *
     *     assert.closeTo(1.5, 1, 0.5, 'numbers are close');
     *
     * @name closeTo
     * @param {Number} actual
     * @param {Number} expected
     * @param {Number} delta
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.closeTo = function (act, exp, delta, msg) {
      new Assertion(act, msg, assert.closeTo, true).to.be.closeTo(exp, delta);
    };

    /**
     * ### .approximately(actual, expected, delta, [message])
     *
     * Asserts that the target is equal `expected`, to within a +/- `delta` range.
     *
     *     assert.approximately(1.5, 1, 0.5, 'numbers are close');
     *
     * @name approximately
     * @param {Number} actual
     * @param {Number} expected
     * @param {Number} delta
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.approximately = function (act, exp, delta, msg) {
      new Assertion(act, msg, assert.approximately, true)
        .to.be.approximately(exp, delta);
    };

    /**
     * ### .sameMembers(set1, set2, [message])
     *
     * Asserts that `set1` and `set2` have the same members in any order. Uses a
     * strict equality check (===).
     *
     *     assert.sameMembers([ 1, 2, 3 ], [ 2, 1, 3 ], 'same members');
     *
     * @name sameMembers
     * @param {Array} set1
     * @param {Array} set2
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.sameMembers = function (set1, set2, msg) {
      new Assertion(set1, msg, assert.sameMembers, true)
        .to.have.same.members(set2);
    }

    /**
     * ### .notSameMembers(set1, set2, [message])
     *
     * Asserts that `set1` and `set2` don't have the same members in any order.
     * Uses a strict equality check (===).
     *
     *     assert.notSameMembers([ 1, 2, 3 ], [ 5, 1, 3 ], 'not same members');
     *
     * @name notSameMembers
     * @param {Array} set1
     * @param {Array} set2
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notSameMembers = function (set1, set2, msg) {
      new Assertion(set1, msg, assert.notSameMembers, true)
        .to.not.have.same.members(set2);
    }

    /**
     * ### .sameDeepMembers(set1, set2, [message])
     *
     * Asserts that `set1` and `set2` have the same members in any order. Uses a
     * deep equality check.
     *
     *     assert.sameDeepMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [{ b: 2 }, { a: 1 }, { c: 3 }], 'same deep members');
     *
     * @name sameDeepMembers
     * @param {Array} set1
     * @param {Array} set2
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.sameDeepMembers = function (set1, set2, msg) {
      new Assertion(set1, msg, assert.sameDeepMembers, true)
        .to.have.same.deep.members(set2);
    }

    /**
     * ### .notSameDeepMembers(set1, set2, [message])
     *
     * Asserts that `set1` and `set2` don't have the same members in any order.
     * Uses a deep equality check.
     *
     *     assert.notSameDeepMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [{ b: 2 }, { a: 1 }, { f: 5 }], 'not same deep members');
     *
     * @name notSameDeepMembers
     * @param {Array} set1
     * @param {Array} set2
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notSameDeepMembers = function (set1, set2, msg) {
      new Assertion(set1, msg, assert.notSameDeepMembers, true)
        .to.not.have.same.deep.members(set2);
    }

    /**
     * ### .sameOrderedMembers(set1, set2, [message])
     *
     * Asserts that `set1` and `set2` have the same members in the same order.
     * Uses a strict equality check (===).
     *
     *     assert.sameOrderedMembers([ 1, 2, 3 ], [ 1, 2, 3 ], 'same ordered members');
     *
     * @name sameOrderedMembers
     * @param {Array} set1
     * @param {Array} set2
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.sameOrderedMembers = function (set1, set2, msg) {
      new Assertion(set1, msg, assert.sameOrderedMembers, true)
        .to.have.same.ordered.members(set2);
    }

    /**
     * ### .notSameOrderedMembers(set1, set2, [message])
     *
     * Asserts that `set1` and `set2` don't have the same members in the same
     * order. Uses a strict equality check (===).
     *
     *     assert.notSameOrderedMembers([ 1, 2, 3 ], [ 2, 1, 3 ], 'not same ordered members');
     *
     * @name notSameOrderedMembers
     * @param {Array} set1
     * @param {Array} set2
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notSameOrderedMembers = function (set1, set2, msg) {
      new Assertion(set1, msg, assert.notSameOrderedMembers, true)
        .to.not.have.same.ordered.members(set2);
    }

    /**
     * ### .sameDeepOrderedMembers(set1, set2, [message])
     *
     * Asserts that `set1` and `set2` have the same members in the same order.
     * Uses a deep equality check.
     *
     * assert.sameDeepOrderedMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [ { a: 1 }, { b: 2 }, { c: 3 } ], 'same deep ordered members');
     *
     * @name sameDeepOrderedMembers
     * @param {Array} set1
     * @param {Array} set2
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.sameDeepOrderedMembers = function (set1, set2, msg) {
      new Assertion(set1, msg, assert.sameDeepOrderedMembers, true)
        .to.have.same.deep.ordered.members(set2);
    }

    /**
     * ### .notSameDeepOrderedMembers(set1, set2, [message])
     *
     * Asserts that `set1` and `set2` don't have the same members in the same
     * order. Uses a deep equality check.
     *
     * assert.notSameDeepOrderedMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [ { a: 1 }, { b: 2 }, { z: 5 } ], 'not same deep ordered members');
     * assert.notSameDeepOrderedMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [ { b: 2 }, { a: 1 }, { c: 3 } ], 'not same deep ordered members');
     *
     * @name notSameDeepOrderedMembers
     * @param {Array} set1
     * @param {Array} set2
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notSameDeepOrderedMembers = function (set1, set2, msg) {
      new Assertion(set1, msg, assert.notSameDeepOrderedMembers, true)
        .to.not.have.same.deep.ordered.members(set2);
    }

    /**
     * ### .includeMembers(superset, subset, [message])
     *
     * Asserts that `subset` is included in `superset` in any order. Uses a
     * strict equality check (===). Duplicates are ignored.
     *
     *     assert.includeMembers([ 1, 2, 3 ], [ 2, 1, 2 ], 'include members');
     *
     * @name includeMembers
     * @param {Array} superset
     * @param {Array} subset
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.includeMembers = function (superset, subset, msg) {
      new Assertion(superset, msg, assert.includeMembers, true)
        .to.include.members(subset);
    }

    /**
     * ### .notIncludeMembers(superset, subset, [message])
     *
     * Asserts that `subset` isn't included in `superset` in any order. Uses a
     * strict equality check (===). Duplicates are ignored.
     *
     *     assert.notIncludeMembers([ 1, 2, 3 ], [ 5, 1 ], 'not include members');
     *
     * @name notIncludeMembers
     * @param {Array} superset
     * @param {Array} subset
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notIncludeMembers = function (superset, subset, msg) {
      new Assertion(superset, msg, assert.notIncludeMembers, true)
        .to.not.include.members(subset);
    }

    /**
     * ### .includeDeepMembers(superset, subset, [message])
     *
     * Asserts that `subset` is included in `superset` in any order. Uses a deep
     * equality check. Duplicates are ignored.
     *
     *     assert.includeDeepMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [ { b: 2 }, { a: 1 }, { b: 2 } ], 'include deep members');
     *
     * @name includeDeepMembers
     * @param {Array} superset
     * @param {Array} subset
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.includeDeepMembers = function (superset, subset, msg) {
      new Assertion(superset, msg, assert.includeDeepMembers, true)
        .to.include.deep.members(subset);
    }

    /**
     * ### .notIncludeDeepMembers(superset, subset, [message])
     *
     * Asserts that `subset` isn't included in `superset` in any order. Uses a
     * deep equality check. Duplicates are ignored.
     *
     *     assert.notIncludeDeepMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [ { b: 2 }, { f: 5 } ], 'not include deep members');
     *
     * @name notIncludeDeepMembers
     * @param {Array} superset
     * @param {Array} subset
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notIncludeDeepMembers = function (superset, subset, msg) {
      new Assertion(superset, msg, assert.notIncludeDeepMembers, true)
        .to.not.include.deep.members(subset);
    }

    /**
     * ### .includeOrderedMembers(superset, subset, [message])
     *
     * Asserts that `subset` is included in `superset` in the same order
     * beginning with the first element in `superset`. Uses a strict equality
     * check (===).
     *
     *     assert.includeOrderedMembers([ 1, 2, 3 ], [ 1, 2 ], 'include ordered members');
     *
     * @name includeOrderedMembers
     * @param {Array} superset
     * @param {Array} subset
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.includeOrderedMembers = function (superset, subset, msg) {
      new Assertion(superset, msg, assert.includeOrderedMembers, true)
        .to.include.ordered.members(subset);
    }

    /**
     * ### .notIncludeOrderedMembers(superset, subset, [message])
     *
     * Asserts that `subset` isn't included in `superset` in the same order
     * beginning with the first element in `superset`. Uses a strict equality
     * check (===).
     *
     *     assert.notIncludeOrderedMembers([ 1, 2, 3 ], [ 2, 1 ], 'not include ordered members');
     *     assert.notIncludeOrderedMembers([ 1, 2, 3 ], [ 2, 3 ], 'not include ordered members');
     *
     * @name notIncludeOrderedMembers
     * @param {Array} superset
     * @param {Array} subset
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notIncludeOrderedMembers = function (superset, subset, msg) {
      new Assertion(superset, msg, assert.notIncludeOrderedMembers, true)
        .to.not.include.ordered.members(subset);
    }

    /**
     * ### .includeDeepOrderedMembers(superset, subset, [message])
     *
     * Asserts that `subset` is included in `superset` in the same order
     * beginning with the first element in `superset`. Uses a deep equality
     * check.
     *
     *     assert.includeDeepOrderedMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [ { a: 1 }, { b: 2 } ], 'include deep ordered members');
     *
     * @name includeDeepOrderedMembers
     * @param {Array} superset
     * @param {Array} subset
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.includeDeepOrderedMembers = function (superset, subset, msg) {
      new Assertion(superset, msg, assert.includeDeepOrderedMembers, true)
        .to.include.deep.ordered.members(subset);
    }

    /**
     * ### .notIncludeDeepOrderedMembers(superset, subset, [message])
     *
     * Asserts that `subset` isn't included in `superset` in the same order
     * beginning with the first element in `superset`. Uses a deep equality
     * check.
     *
     *     assert.notIncludeDeepOrderedMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [ { a: 1 }, { f: 5 } ], 'not include deep ordered members');
     *     assert.notIncludeDeepOrderedMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [ { b: 2 }, { a: 1 } ], 'not include deep ordered members');
     *     assert.notIncludeDeepOrderedMembers([ { a: 1 }, { b: 2 }, { c: 3 } ], [ { b: 2 }, { c: 3 } ], 'not include deep ordered members');
     *
     * @name notIncludeDeepOrderedMembers
     * @param {Array} superset
     * @param {Array} subset
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.notIncludeDeepOrderedMembers = function (superset, subset, msg) {
      new Assertion(superset, msg, assert.notIncludeDeepOrderedMembers, true)
        .to.not.include.deep.ordered.members(subset);
    }

    /**
     * ### .oneOf(inList, list, [message])
     *
     * Asserts that non-object, non-array value `inList` appears in the flat array `list`.
     *
     *     assert.oneOf(1, [ 2, 1 ], 'Not found in list');
     *
     * @name oneOf
     * @param {*} inList
     * @param {Array<*>} list
     * @param {String} message
     * @namespace Assert
     * @api public
     */

    assert.oneOf = function (inList, list, msg) {
      new Assertion(inList, msg, assert.oneOf, true).to.be.oneOf(list);
    }

    /**
     * ### .changes(function, object, property, [message])
     *
     * Asserts that a function changes the value of a property.
     *
     *     var obj = { val: 10 };
     *     var fn = function() { obj.val = 22 };
     *     assert.changes(fn, obj, 'val');
     *
     * @name changes
     * @param {Function} modifier function
     * @param {Object} object or getter function
     * @param {String} property name _optional_
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.changes = function (fn, obj, prop, msg) {
      if (arguments.length === 3 && typeof obj === 'function') {
        msg = prop;
        prop = null;
      }

      new Assertion(fn, msg, assert.changes, true).to.change(obj, prop);
    }

     /**
     * ### .changesBy(function, object, property, delta, [message])
     *
     * Asserts that a function changes the value of a property by an amount (delta).
     *
     *     var obj = { val: 10 };
     *     var fn = function() { obj.val += 2 };
     *     assert.changesBy(fn, obj, 'val', 2);
     *
     * @name changesBy
     * @param {Function} modifier function
     * @param {Object} object or getter function
     * @param {String} property name _optional_
     * @param {Number} change amount (delta)
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.changesBy = function (fn, obj, prop, delta, msg) {
      if (arguments.length === 4 && typeof obj === 'function') {
        var tmpMsg = delta;
        delta = prop;
        msg = tmpMsg;
      } else if (arguments.length === 3) {
        delta = prop;
        prop = null;
      }

      new Assertion(fn, msg, assert.changesBy, true)
        .to.change(obj, prop).by(delta);
    }

     /**
     * ### .doesNotChange(function, object, property, [message])
     *
     * Asserts that a function does not change the value of a property.
     *
     *     var obj = { val: 10 };
     *     var fn = function() { console.log('foo'); };
     *     assert.doesNotChange(fn, obj, 'val');
     *
     * @name doesNotChange
     * @param {Function} modifier function
     * @param {Object} object or getter function
     * @param {String} property name _optional_
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.doesNotChange = function (fn, obj, prop, msg) {
      if (arguments.length === 3 && typeof obj === 'function') {
        msg = prop;
        prop = null;
      }

      return new Assertion(fn, msg, assert.doesNotChange, true)
        .to.not.change(obj, prop);
    }

    /**
     * ### .changesButNotBy(function, object, property, delta, [message])
     *
     * Asserts that a function does not change the value of a property or of a function's return value by an amount (delta)
     *
     *     var obj = { val: 10 };
     *     var fn = function() { obj.val += 10 };
     *     assert.changesButNotBy(fn, obj, 'val', 5);
     *
     * @name changesButNotBy
     * @param {Function} modifier function
     * @param {Object} object or getter function
     * @param {String} property name _optional_
     * @param {Number} change amount (delta)
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.changesButNotBy = function (fn, obj, prop, delta, msg) {
      if (arguments.length === 4 && typeof obj === 'function') {
        var tmpMsg = delta;
        delta = prop;
        msg = tmpMsg;
      } else if (arguments.length === 3) {
        delta = prop;
        prop = null;
      }

      new Assertion(fn, msg, assert.changesButNotBy, true)
        .to.change(obj, prop).but.not.by(delta);
    }

    /**
     * ### .increases(function, object, property, [message])
     *
     * Asserts that a function increases a numeric object property.
     *
     *     var obj = { val: 10 };
     *     var fn = function() { obj.val = 13 };
     *     assert.increases(fn, obj, 'val');
     *
     * @name increases
     * @param {Function} modifier function
     * @param {Object} object or getter function
     * @param {String} property name _optional_
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.increases = function (fn, obj, prop, msg) {
      if (arguments.length === 3 && typeof obj === 'function') {
        msg = prop;
        prop = null;
      }

      return new Assertion(fn, msg, assert.increases, true)
        .to.increase(obj, prop);
    }

    /**
     * ### .increasesBy(function, object, property, delta, [message])
     *
     * Asserts that a function increases a numeric object property or a function's return value by an amount (delta).
     *
     *     var obj = { val: 10 };
     *     var fn = function() { obj.val += 10 };
     *     assert.increasesBy(fn, obj, 'val', 10);
     *
     * @name increasesBy
     * @param {Function} modifier function
     * @param {Object} object or getter function
     * @param {String} property name _optional_
     * @param {Number} change amount (delta)
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.increasesBy = function (fn, obj, prop, delta, msg) {
      if (arguments.length === 4 && typeof obj === 'function') {
        var tmpMsg = delta;
        delta = prop;
        msg = tmpMsg;
      } else if (arguments.length === 3) {
        delta = prop;
        prop = null;
      }

      new Assertion(fn, msg, assert.increasesBy, true)
        .to.increase(obj, prop).by(delta);
    }

    /**
     * ### .doesNotIncrease(function, object, property, [message])
     *
     * Asserts that a function does not increase a numeric object property.
     *
     *     var obj = { val: 10 };
     *     var fn = function() { obj.val = 8 };
     *     assert.doesNotIncrease(fn, obj, 'val');
     *
     * @name doesNotIncrease
     * @param {Function} modifier function
     * @param {Object} object or getter function
     * @param {String} property name _optional_
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.doesNotIncrease = function (fn, obj, prop, msg) {
      if (arguments.length === 3 && typeof obj === 'function') {
        msg = prop;
        prop = null;
      }

      return new Assertion(fn, msg, assert.doesNotIncrease, true)
        .to.not.increase(obj, prop);
    }

    /**
     * ### .increasesButNotBy(function, object, property, [message])
     *
     * Asserts that a function does not increase a numeric object property or function's return value by an amount (delta).
     *
     *     var obj = { val: 10 };
     *     var fn = function() { obj.val = 15 };
     *     assert.increasesButNotBy(fn, obj, 'val', 10);
     *
     * @name increasesButNotBy
     * @param {Function} modifier function
     * @param {Object} object or getter function
     * @param {String} property name _optional_
     * @param {Number} change amount (delta)
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.increasesButNotBy = function (fn, obj, prop, delta, msg) {
      if (arguments.length === 4 && typeof obj === 'function') {
        var tmpMsg = delta;
        delta = prop;
        msg = tmpMsg;
      } else if (arguments.length === 3) {
        delta = prop;
        prop = null;
      }

      new Assertion(fn, msg, assert.increasesButNotBy, true)
        .to.increase(obj, prop).but.not.by(delta);
    }

    /**
     * ### .decreases(function, object, property, [message])
     *
     * Asserts that a function decreases a numeric object property.
     *
     *     var obj = { val: 10 };
     *     var fn = function() { obj.val = 5 };
     *     assert.decreases(fn, obj, 'val');
     *
     * @name decreases
     * @param {Function} modifier function
     * @param {Object} object or getter function
     * @param {String} property name _optional_
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.decreases = function (fn, obj, prop, msg) {
      if (arguments.length === 3 && typeof obj === 'function') {
        msg = prop;
        prop = null;
      }

      return new Assertion(fn, msg, assert.decreases, true)
        .to.decrease(obj, prop);
    }

    /**
     * ### .decreasesBy(function, object, property, delta, [message])
     *
     * Asserts that a function decreases a numeric object property or a function's return value by an amount (delta)
     *
     *     var obj = { val: 10 };
     *     var fn = function() { obj.val -= 5 };
     *     assert.decreasesBy(fn, obj, 'val', 5);
     *
     * @name decreasesBy
     * @param {Function} modifier function
     * @param {Object} object or getter function
     * @param {String} property name _optional_
     * @param {Number} change amount (delta)
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.decreasesBy = function (fn, obj, prop, delta, msg) {
      if (arguments.length === 4 && typeof obj === 'function') {
        var tmpMsg = delta;
        delta = prop;
        msg = tmpMsg;
      } else if (arguments.length === 3) {
        delta = prop;
        prop = null;
      }

      new Assertion(fn, msg, assert.decreasesBy, true)
        .to.decrease(obj, prop).by(delta);
    }

    /**
     * ### .doesNotDecrease(function, object, property, [message])
     *
     * Asserts that a function does not decreases a numeric object property.
     *
     *     var obj = { val: 10 };
     *     var fn = function() { obj.val = 15 };
     *     assert.doesNotDecrease(fn, obj, 'val');
     *
     * @name doesNotDecrease
     * @param {Function} modifier function
     * @param {Object} object or getter function
     * @param {String} property name _optional_
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.doesNotDecrease = function (fn, obj, prop, msg) {
      if (arguments.length === 3 && typeof obj === 'function') {
        msg = prop;
        prop = null;
      }

      return new Assertion(fn, msg, assert.doesNotDecrease, true)
        .to.not.decrease(obj, prop);
    }

    /**
     * ### .doesNotDecreaseBy(function, object, property, delta, [message])
     *
     * Asserts that a function does not decreases a numeric object property or a function's return value by an amount (delta)
     *
     *     var obj = { val: 10 };
     *     var fn = function() { obj.val = 5 };
     *     assert.doesNotDecreaseBy(fn, obj, 'val', 1);
     *
     * @name doesNotDecrease
     * @param {Function} modifier function
     * @param {Object} object or getter function
     * @param {String} property name _optional_
     * @param {Number} change amount (delta)
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.doesNotDecreaseBy = function (fn, obj, prop, delta, msg) {
      if (arguments.length === 4 && typeof obj === 'function') {
        var tmpMsg = delta;
        delta = prop;
        msg = tmpMsg;
      } else if (arguments.length === 3) {
        delta = prop;
        prop = null;
      }

      return new Assertion(fn, msg, assert.doesNotDecreaseBy, true)
        .to.not.decrease(obj, prop).by(delta);
    }

    /**
     * ### .decreasesButNotBy(function, object, property, delta, [message])
     *
     * Asserts that a function does not decreases a numeric object property or a function's return value by an amount (delta)
     *
     *     var obj = { val: 10 };
     *     var fn = function() { obj.val = 5 };
     *     assert.decreasesButNotBy(fn, obj, 'val', 1);
     *
     * @name decreasesButNotBy
     * @param {Function} modifier function
     * @param {Object} object or getter function
     * @param {String} property name _optional_
     * @param {Number} change amount (delta)
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.decreasesButNotBy = function (fn, obj, prop, delta, msg) {
      if (arguments.length === 4 && typeof obj === 'function') {
        var tmpMsg = delta;
        delta = prop;
        msg = tmpMsg;
      } else if (arguments.length === 3) {
        delta = prop;
        prop = null;
      }

      new Assertion(fn, msg, assert.decreasesButNotBy, true)
        .to.decrease(obj, prop).but.not.by(delta);
    }

    /*!
     * ### .ifError(object)
     *
     * Asserts if value is not a false value, and throws if it is a true value.
     * This is added to allow for chai to be a drop-in replacement for Node's
     * assert class.
     *
     *     var err = new Error('I am a custom error');
     *     assert.ifError(err); // Rethrows err!
     *
     * @name ifError
     * @param {Object} object
     * @namespace Assert
     * @api public
     */

    assert.ifError = function (val) {
      if (val) {
        throw(val);
      }
    };

    /**
     * ### .isExtensible(object)
     *
     * Asserts that `object` is extensible (can have new properties added to it).
     *
     *     assert.isExtensible({});
     *
     * @name isExtensible
     * @alias extensible
     * @param {Object} object
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.isExtensible = function (obj, msg) {
      new Assertion(obj, msg, assert.isExtensible, true).to.be.extensible;
    };

    /**
     * ### .isNotExtensible(object)
     *
     * Asserts that `object` is _not_ extensible.
     *
     *     var nonExtensibleObject = Object.preventExtensions({});
     *     var sealedObject = Object.seal({});
     *     var frozenObject = Object.freeze({});
     *
     *     assert.isNotExtensible(nonExtensibleObject);
     *     assert.isNotExtensible(sealedObject);
     *     assert.isNotExtensible(frozenObject);
     *
     * @name isNotExtensible
     * @alias notExtensible
     * @param {Object} object
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.isNotExtensible = function (obj, msg) {
      new Assertion(obj, msg, assert.isNotExtensible, true).to.not.be.extensible;
    };

    /**
     * ### .isSealed(object)
     *
     * Asserts that `object` is sealed (cannot have new properties added to it
     * and its existing properties cannot be removed).
     *
     *     var sealedObject = Object.seal({});
     *     var frozenObject = Object.seal({});
     *
     *     assert.isSealed(sealedObject);
     *     assert.isSealed(frozenObject);
     *
     * @name isSealed
     * @alias sealed
     * @param {Object} object
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.isSealed = function (obj, msg) {
      new Assertion(obj, msg, assert.isSealed, true).to.be.sealed;
    };

    /**
     * ### .isNotSealed(object)
     *
     * Asserts that `object` is _not_ sealed.
     *
     *     assert.isNotSealed({});
     *
     * @name isNotSealed
     * @alias notSealed
     * @param {Object} object
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.isNotSealed = function (obj, msg) {
      new Assertion(obj, msg, assert.isNotSealed, true).to.not.be.sealed;
    };

    /**
     * ### .isFrozen(object)
     *
     * Asserts that `object` is frozen (cannot have new properties added to it
     * and its existing properties cannot be modified).
     *
     *     var frozenObject = Object.freeze({});
     *     assert.frozen(frozenObject);
     *
     * @name isFrozen
     * @alias frozen
     * @param {Object} object
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.isFrozen = function (obj, msg) {
      new Assertion(obj, msg, assert.isFrozen, true).to.be.frozen;
    };

    /**
     * ### .isNotFrozen(object)
     *
     * Asserts that `object` is _not_ frozen.
     *
     *     assert.isNotFrozen({});
     *
     * @name isNotFrozen
     * @alias notFrozen
     * @param {Object} object
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.isNotFrozen = function (obj, msg) {
      new Assertion(obj, msg, assert.isNotFrozen, true).to.not.be.frozen;
    };

    /**
     * ### .isEmpty(target)
     *
     * Asserts that the target does not contain any values.
     * For arrays and strings, it checks the `length` property.
     * For `Map` and `Set` instances, it checks the `size` property.
     * For non-function objects, it gets the count of own
     * enumerable string keys.
     *
     *     assert.isEmpty([]);
     *     assert.isEmpty('');
     *     assert.isEmpty(new Map);
     *     assert.isEmpty({});
     *
     * @name isEmpty
     * @alias empty
     * @param {Object|Array|String|Map|Set} target
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.isEmpty = function(val, msg) {
      new Assertion(val, msg, assert.isEmpty, true).to.be.empty;
    };

    /**
     * ### .isNotEmpty(target)
     *
     * Asserts that the target contains values.
     * For arrays and strings, it checks the `length` property.
     * For `Map` and `Set` instances, it checks the `size` property.
     * For non-function objects, it gets the count of own
     * enumerable string keys.
     *
     *     assert.isNotEmpty([1, 2]);
     *     assert.isNotEmpty('34');
     *     assert.isNotEmpty(new Set([5, 6]));
     *     assert.isNotEmpty({ key: 7 });
     *
     * @name isNotEmpty
     * @alias notEmpty
     * @param {Object|Array|String|Map|Set} target
     * @param {String} message _optional_
     * @namespace Assert
     * @api public
     */

    assert.isNotEmpty = function(val, msg) {
      new Assertion(val, msg, assert.isNotEmpty, true).to.not.be.empty;
    };

    /*!
     * Aliases.
     */

    (function alias(name, as){
      assert[as] = assert[name];
      return alias;
    })
    ('isOk', 'ok')
    ('isNotOk', 'notOk')
    ('throws', 'throw')
    ('throws', 'Throw')
    ('isExtensible', 'extensible')
    ('isNotExtensible', 'notExtensible')
    ('isSealed', 'sealed')
    ('isNotSealed', 'notSealed')
    ('isFrozen', 'frozen')
    ('isNotFrozen', 'notFrozen')
    ('isEmpty', 'empty')
    ('isNotEmpty', 'notEmpty');
  };

  },{}],7:[function(require,module,exports){
  /*!
   * chai
   * Copyright(c) 2011-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  module.exports = function (chai, util) {
    chai.expect = function (val, message) {
      return new chai.Assertion(val, message);
    };

    /**
     * ### .fail(actual, expected, [message], [operator])
     *
     * Throw a failure.
     *
     * @name fail
     * @param {Mixed} actual
     * @param {Mixed} expected
     * @param {String} message
     * @param {String} operator
     * @namespace BDD
     * @api public
     */

    chai.expect.fail = function (actual, expected, message, operator) {
      message = message || 'expect.fail()';
      throw new chai.AssertionError(message, {
          actual: actual
        , expected: expected
        , operator: operator
      }, chai.expect.fail);
    };
  };

  },{}],8:[function(require,module,exports){
  /*!
   * chai
   * Copyright(c) 2011-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  module.exports = function (chai, util) {
    var Assertion = chai.Assertion;

    function loadShould () {
      // explicitly define this method as function as to have it's name to include as `ssfi`
      function shouldGetter() {
        if (this instanceof String
            || this instanceof Number
            || this instanceof Boolean
            || typeof Symbol === 'function' && this instanceof Symbol) {
          return new Assertion(this.valueOf(), null, shouldGetter);
        }
        return new Assertion(this, null, shouldGetter);
      }
      function shouldSetter(value) {
        // See https://github.com/chaijs/chai/issues/86: this makes
        // `whatever.should = someValue` actually set `someValue`, which is
        // especially useful for `global.should = require('chai').should()`.
        //
        // Note that we have to use [[DefineProperty]] instead of [[Put]]
        // since otherwise we would trigger this very setter!
        Object.defineProperty(this, 'should', {
          value: value,
          enumerable: true,
          configurable: true,
          writable: true
        });
      }
      // modify Object.prototype to have `should`
      Object.defineProperty(Object.prototype, 'should', {
        set: shouldSetter
        , get: shouldGetter
        , configurable: true
      });

      var should = {};

      /**
       * ### .fail(actual, expected, [message], [operator])
       *
       * Throw a failure.
       *
       * @name fail
       * @param {Mixed} actual
       * @param {Mixed} expected
       * @param {String} message
       * @param {String} operator
       * @namespace BDD
       * @api public
       */

      should.fail = function (actual, expected, message, operator) {
        message = message || 'should.fail()';
        throw new chai.AssertionError(message, {
            actual: actual
          , expected: expected
          , operator: operator
        }, should.fail);
      };

      /**
       * ### .equal(actual, expected, [message])
       *
       * Asserts non-strict equality (`==`) of `actual` and `expected`.
       *
       *     should.equal(3, '3', '== coerces values to strings');
       *
       * @name equal
       * @param {Mixed} actual
       * @param {Mixed} expected
       * @param {String} message
       * @namespace Should
       * @api public
       */

      should.equal = function (val1, val2, msg) {
        new Assertion(val1, msg).to.equal(val2);
      };

      /**
       * ### .throw(function, [constructor/string/regexp], [string/regexp], [message])
       *
       * Asserts that `function` will throw an error that is an instance of
       * `constructor`, or alternately that it will throw an error with message
       * matching `regexp`.
       *
       *     should.throw(fn, 'function throws a reference error');
       *     should.throw(fn, /function throws a reference error/);
       *     should.throw(fn, ReferenceError);
       *     should.throw(fn, ReferenceError, 'function throws a reference error');
       *     should.throw(fn, ReferenceError, /function throws a reference error/);
       *
       * @name throw
       * @alias Throw
       * @param {Function} function
       * @param {ErrorConstructor} constructor
       * @param {RegExp} regexp
       * @param {String} message
       * @see https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Error#Error_types
       * @namespace Should
       * @api public
       */

      should.Throw = function (fn, errt, errs, msg) {
        new Assertion(fn, msg).to.Throw(errt, errs);
      };

      /**
       * ### .exist
       *
       * Asserts that the target is neither `null` nor `undefined`.
       *
       *     var foo = 'hi';
       *
       *     should.exist(foo, 'foo exists');
       *
       * @name exist
       * @namespace Should
       * @api public
       */

      should.exist = function (val, msg) {
        new Assertion(val, msg).to.exist;
      }

      // negation
      should.not = {}

      /**
       * ### .not.equal(actual, expected, [message])
       *
       * Asserts non-strict inequality (`!=`) of `actual` and `expected`.
       *
       *     should.not.equal(3, 4, 'these numbers are not equal');
       *
       * @name not.equal
       * @param {Mixed} actual
       * @param {Mixed} expected
       * @param {String} message
       * @namespace Should
       * @api public
       */

      should.not.equal = function (val1, val2, msg) {
        new Assertion(val1, msg).to.not.equal(val2);
      };

      /**
       * ### .throw(function, [constructor/regexp], [message])
       *
       * Asserts that `function` will _not_ throw an error that is an instance of
       * `constructor`, or alternately that it will not throw an error with message
       * matching `regexp`.
       *
       *     should.not.throw(fn, Error, 'function does not throw');
       *
       * @name not.throw
       * @alias not.Throw
       * @param {Function} function
       * @param {ErrorConstructor} constructor
       * @param {RegExp} regexp
       * @param {String} message
       * @see https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Error#Error_types
       * @namespace Should
       * @api public
       */

      should.not.Throw = function (fn, errt, errs, msg) {
        new Assertion(fn, msg).to.not.Throw(errt, errs);
      };

      /**
       * ### .not.exist
       *
       * Asserts that the target is neither `null` nor `undefined`.
       *
       *     var bar = null;
       *
       *     should.not.exist(bar, 'bar does not exist');
       *
       * @name not.exist
       * @namespace Should
       * @api public
       */

      should.not.exist = function (val, msg) {
        new Assertion(val, msg).to.not.exist;
      }

      should['throw'] = should['Throw'];
      should.not['throw'] = should.not['Throw'];

      return should;
    };

    chai.should = loadShould;
    chai.Should = loadShould;
  };

  },{}],9:[function(require,module,exports){
  /*!
   * Chai - addChainingMethod utility
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /*!
   * Module dependencies
   */

  var addLengthGuard = require('./addLengthGuard');
  var chai = require('../../chai');
  var flag = require('./flag');
  var proxify = require('./proxify');
  var transferFlags = require('./transferFlags');

  /*!
   * Module variables
   */

  // Check whether `Object.setPrototypeOf` is supported
  var canSetPrototype = typeof Object.setPrototypeOf === 'function';

  // Without `Object.setPrototypeOf` support, this module will need to add properties to a function.
  // However, some of functions' own props are not configurable and should be skipped.
  var testFn = function() {};
  var excludeNames = Object.getOwnPropertyNames(testFn).filter(function(name) {
    var propDesc = Object.getOwnPropertyDescriptor(testFn, name);

    // Note: PhantomJS 1.x includes `callee` as one of `testFn`'s own properties,
    // but then returns `undefined` as the property descriptor for `callee`. As a
    // workaround, we perform an otherwise unnecessary type-check for `propDesc`,
    // and then filter it out if it's not an object as it should be.
    if (typeof propDesc !== 'object')
      return true;

    return !propDesc.configurable;
  });

  // Cache `Function` properties
  var call  = Function.prototype.call,
      apply = Function.prototype.apply;

  /**
   * ### .addChainableMethod(ctx, name, method, chainingBehavior)
   *
   * Adds a method to an object, such that the method can also be chained.
   *
   *     utils.addChainableMethod(chai.Assertion.prototype, 'foo', function (str) {
   *       var obj = utils.flag(this, 'object');
   *       new chai.Assertion(obj).to.be.equal(str);
   *     });
   *
   * Can also be accessed directly from `chai.Assertion`.
   *
   *     chai.Assertion.addChainableMethod('foo', fn, chainingBehavior);
   *
   * The result can then be used as both a method assertion, executing both `method` and
   * `chainingBehavior`, or as a language chain, which only executes `chainingBehavior`.
   *
   *     expect(fooStr).to.be.foo('bar');
   *     expect(fooStr).to.be.foo.equal('foo');
   *
   * @param {Object} ctx object to which the method is added
   * @param {String} name of method to add
   * @param {Function} method function to be used for `name`, when called
   * @param {Function} chainingBehavior function to be called every time the property is accessed
   * @namespace Utils
   * @name addChainableMethod
   * @api public
   */

  module.exports = function addChainableMethod(ctx, name, method, chainingBehavior) {
    if (typeof chainingBehavior !== 'function') {
      chainingBehavior = function () { };
    }

    var chainableBehavior = {
        method: method
      , chainingBehavior: chainingBehavior
    };

    // save the methods so we can overwrite them later, if we need to.
    if (!ctx.__methods) {
      ctx.__methods = {};
    }
    ctx.__methods[name] = chainableBehavior;

    Object.defineProperty(ctx, name,
      { get: function chainableMethodGetter() {
          chainableBehavior.chainingBehavior.call(this);

          var chainableMethodWrapper = function () {
            // Setting the `ssfi` flag to `chainableMethodWrapper` causes this
            // function to be the starting point for removing implementation
            // frames from the stack trace of a failed assertion.
            //
            // However, we only want to use this function as the starting point if
            // the `lockSsfi` flag isn't set.
            //
            // If the `lockSsfi` flag is set, then this assertion is being
            // invoked from inside of another assertion. In this case, the `ssfi`
            // flag has already been set by the outer assertion.
            //
            // Note that overwriting a chainable method merely replaces the saved
            // methods in `ctx.__methods` instead of completely replacing the
            // overwritten assertion. Therefore, an overwriting assertion won't
            // set the `ssfi` or `lockSsfi` flags.
            if (!flag(this, 'lockSsfi')) {
              flag(this, 'ssfi', chainableMethodWrapper);
            }

            var result = chainableBehavior.method.apply(this, arguments);
            if (result !== undefined) {
              return result;
            }

            var newAssertion = new chai.Assertion();
            transferFlags(this, newAssertion);
            return newAssertion;
          };

          addLengthGuard(chainableMethodWrapper, name, true);

          // Use `Object.setPrototypeOf` if available
          if (canSetPrototype) {
            // Inherit all properties from the object by replacing the `Function` prototype
            var prototype = Object.create(this);
            // Restore the `call` and `apply` methods from `Function`
            prototype.call = call;
            prototype.apply = apply;
            Object.setPrototypeOf(chainableMethodWrapper, prototype);
          }
          // Otherwise, redefine all properties (slow!)
          else {
            var asserterNames = Object.getOwnPropertyNames(ctx);
            asserterNames.forEach(function (asserterName) {
              if (excludeNames.indexOf(asserterName) !== -1) {
                return;
              }

              var pd = Object.getOwnPropertyDescriptor(ctx, asserterName);
              Object.defineProperty(chainableMethodWrapper, asserterName, pd);
            });
          }

          transferFlags(this, chainableMethodWrapper);
          return proxify(chainableMethodWrapper);
        }
      , configurable: true
    });
  };

  },{"../../chai":2,"./addLengthGuard":10,"./flag":15,"./proxify":30,"./transferFlags":32}],10:[function(require,module,exports){
  var config = require('../config');

  var fnLengthDesc = Object.getOwnPropertyDescriptor(function () {}, 'length');

  /*!
   * Chai - addLengthGuard utility
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /**
   * ### .addLengthGuard(fn, assertionName, isChainable)
   *
   * Define `length` as a getter on the given uninvoked method assertion. The
   * getter acts as a guard against chaining `length` directly off of an uninvoked
   * method assertion, which is a problem because it references `function`'s
   * built-in `length` property instead of Chai's `length` assertion. When the
   * getter catches the user making this mistake, it throws an error with a
   * helpful message.
   *
   * There are two ways in which this mistake can be made. The first way is by
   * chaining the `length` assertion directly off of an uninvoked chainable
   * method. In this case, Chai suggests that the user use `lengthOf` instead. The
   * second way is by chaining the `length` assertion directly off of an uninvoked
   * non-chainable method. Non-chainable methods must be invoked prior to
   * chaining. In this case, Chai suggests that the user consult the docs for the
   * given assertion.
   *
   * If the `length` property of functions is unconfigurable, then return `fn`
   * without modification.
   *
   * Note that in ES6, the function's `length` property is configurable, so once
   * support for legacy environments is dropped, Chai's `length` property can
   * replace the built-in function's `length` property, and this length guard will
   * no longer be necessary. In the mean time, maintaining consistency across all
   * environments is the priority.
   *
   * @param {Function} fn
   * @param {String} assertionName
   * @param {Boolean} isChainable
   * @namespace Utils
   * @name addLengthGuard
   */

  module.exports = function addLengthGuard (fn, assertionName, isChainable) {
    if (!fnLengthDesc.configurable) return fn;

    Object.defineProperty(fn, 'length', {
      get: function () {
        if (isChainable) {
          throw Error('Invalid Chai property: ' + assertionName + '.length. Due' +
            ' to a compatibility issue, "length" cannot directly follow "' +
            assertionName + '". Use "' + assertionName + '.lengthOf" instead.');
        }

        throw Error('Invalid Chai property: ' + assertionName + '.length. See' +
          ' docs for proper usage of "' + assertionName + '".');
      }
    });

    return fn;
  };

  },{"../config":4}],11:[function(require,module,exports){
  /*!
   * Chai - addMethod utility
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  var addLengthGuard = require('./addLengthGuard');
  var chai = require('../../chai');
  var flag = require('./flag');
  var proxify = require('./proxify');
  var transferFlags = require('./transferFlags');

  /**
   * ### .addMethod(ctx, name, method)
   *
   * Adds a method to the prototype of an object.
   *
   *     utils.addMethod(chai.Assertion.prototype, 'foo', function (str) {
   *       var obj = utils.flag(this, 'object');
   *       new chai.Assertion(obj).to.be.equal(str);
   *     });
   *
   * Can also be accessed directly from `chai.Assertion`.
   *
   *     chai.Assertion.addMethod('foo', fn);
   *
   * Then can be used as any other assertion.
   *
   *     expect(fooStr).to.be.foo('bar');
   *
   * @param {Object} ctx object to which the method is added
   * @param {String} name of method to add
   * @param {Function} method function to be used for name
   * @namespace Utils
   * @name addMethod
   * @api public
   */

  module.exports = function addMethod(ctx, name, method) {
    var methodWrapper = function () {
      // Setting the `ssfi` flag to `methodWrapper` causes this function to be the
      // starting point for removing implementation frames from the stack trace of
      // a failed assertion.
      //
      // However, we only want to use this function as the starting point if the
      // `lockSsfi` flag isn't set.
      //
      // If the `lockSsfi` flag is set, then either this assertion has been
      // overwritten by another assertion, or this assertion is being invoked from
      // inside of another assertion. In the first case, the `ssfi` flag has
      // already been set by the overwriting assertion. In the second case, the
      // `ssfi` flag has already been set by the outer assertion.
      if (!flag(this, 'lockSsfi')) {
        flag(this, 'ssfi', methodWrapper);
      }

      var result = method.apply(this, arguments);
      if (result !== undefined)
        return result;

      var newAssertion = new chai.Assertion();
      transferFlags(this, newAssertion);
      return newAssertion;
    };

    addLengthGuard(methodWrapper, name, false);
    ctx[name] = proxify(methodWrapper, name);
  };

  },{"../../chai":2,"./addLengthGuard":10,"./flag":15,"./proxify":30,"./transferFlags":32}],12:[function(require,module,exports){
  /*!
   * Chai - addProperty utility
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  var chai = require('../../chai');
  var flag = require('./flag');
  var isProxyEnabled = require('./isProxyEnabled');
  var transferFlags = require('./transferFlags');

  /**
   * ### .addProperty(ctx, name, getter)
   *
   * Adds a property to the prototype of an object.
   *
   *     utils.addProperty(chai.Assertion.prototype, 'foo', function () {
   *       var obj = utils.flag(this, 'object');
   *       new chai.Assertion(obj).to.be.instanceof(Foo);
   *     });
   *
   * Can also be accessed directly from `chai.Assertion`.
   *
   *     chai.Assertion.addProperty('foo', fn);
   *
   * Then can be used as any other assertion.
   *
   *     expect(myFoo).to.be.foo;
   *
   * @param {Object} ctx object to which the property is added
   * @param {String} name of property to add
   * @param {Function} getter function to be used for name
   * @namespace Utils
   * @name addProperty
   * @api public
   */

  module.exports = function addProperty(ctx, name, getter) {
    getter = getter === undefined ? function () {} : getter;

    Object.defineProperty(ctx, name,
      { get: function propertyGetter() {
          // Setting the `ssfi` flag to `propertyGetter` causes this function to
          // be the starting point for removing implementation frames from the
          // stack trace of a failed assertion.
          //
          // However, we only want to use this function as the starting point if
          // the `lockSsfi` flag isn't set and proxy protection is disabled.
          //
          // If the `lockSsfi` flag is set, then either this assertion has been
          // overwritten by another assertion, or this assertion is being invoked
          // from inside of another assertion. In the first case, the `ssfi` flag
          // has already been set by the overwriting assertion. In the second
          // case, the `ssfi` flag has already been set by the outer assertion.
          //
          // If proxy protection is enabled, then the `ssfi` flag has already been
          // set by the proxy getter.
          if (!isProxyEnabled() && !flag(this, 'lockSsfi')) {
            flag(this, 'ssfi', propertyGetter);
          }

          var result = getter.call(this);
          if (result !== undefined)
            return result;

          var newAssertion = new chai.Assertion();
          transferFlags(this, newAssertion);
          return newAssertion;
        }
      , configurable: true
    });
  };

  },{"../../chai":2,"./flag":15,"./isProxyEnabled":25,"./transferFlags":32}],13:[function(require,module,exports){
  /*!
   * Chai - compareByInspect utility
   * Copyright(c) 2011-2016 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /*!
   * Module dependancies
   */

  var inspect = require('./inspect');

  /**
   * ### .compareByInspect(mixed, mixed)
   *
   * To be used as a compareFunction with Array.prototype.sort. Compares elements
   * using inspect instead of default behavior of using toString so that Symbols
   * and objects with irregular/missing toString can still be sorted without a
   * TypeError.
   *
   * @param {Mixed} first element to compare
   * @param {Mixed} second element to compare
   * @returns {Number} -1 if 'a' should come before 'b'; otherwise 1
   * @name compareByInspect
   * @namespace Utils
   * @api public
   */

  module.exports = function compareByInspect(a, b) {
    return inspect(a) < inspect(b) ? -1 : 1;
  };

  },{"./inspect":23}],14:[function(require,module,exports){
  /*!
   * Chai - expectTypes utility
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /**
   * ### .expectTypes(obj, types)
   *
   * Ensures that the object being tested against is of a valid type.
   *
   *     utils.expectTypes(this, ['array', 'object', 'string']);
   *
   * @param {Mixed} obj constructed Assertion
   * @param {Array} type A list of allowed types for this assertion
   * @namespace Utils
   * @name expectTypes
   * @api public
   */

  var AssertionError = require('assertion-error');
  var flag = require('./flag');
  var type = require('type-detect');

  module.exports = function expectTypes(obj, types) {
    var flagMsg = flag(obj, 'message');
    var ssfi = flag(obj, 'ssfi');

    flagMsg = flagMsg ? flagMsg + ': ' : '';

    obj = flag(obj, 'object');
    types = types.map(function (t) { return t.toLowerCase(); });
    types.sort();

    // Transforms ['lorem', 'ipsum'] into 'a lorem, or an ipsum'
    var str = types.map(function (t, index) {
      var art = ~[ 'a', 'e', 'i', 'o', 'u' ].indexOf(t.charAt(0)) ? 'an' : 'a';
      var or = types.length > 1 && index === types.length - 1 ? 'or ' : '';
      return or + art + ' ' + t;
    }).join(', ');

    var objType = type(obj).toLowerCase();

    if (!types.some(function (expected) { return objType === expected; })) {
      throw new AssertionError(
        flagMsg + 'object tested must be ' + str + ', but ' + objType + ' given',
        undefined,
        ssfi
      );
    }
  };

  },{"./flag":15,"assertion-error":33,"type-detect":38}],15:[function(require,module,exports){
  /*!
   * Chai - flag utility
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /**
   * ### .flag(object, key, [value])
   *
   * Get or set a flag value on an object. If a
   * value is provided it will be set, else it will
   * return the currently set value or `undefined` if
   * the value is not set.
   *
   *     utils.flag(this, 'foo', 'bar'); // setter
   *     utils.flag(this, 'foo'); // getter, returns `bar`
   *
   * @param {Object} object constructed Assertion
   * @param {String} key
   * @param {Mixed} value (optional)
   * @namespace Utils
   * @name flag
   * @api private
   */

  module.exports = function flag(obj, key, value) {
    var flags = obj.__flags || (obj.__flags = Object.create(null));
    if (arguments.length === 3) {
      flags[key] = value;
    } else {
      return flags[key];
    }
  };

  },{}],16:[function(require,module,exports){
  /*!
   * Chai - getActual utility
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /**
   * ### .getActual(object, [actual])
   *
   * Returns the `actual` value for an Assertion.
   *
   * @param {Object} object (constructed Assertion)
   * @param {Arguments} chai.Assertion.prototype.assert arguments
   * @namespace Utils
   * @name getActual
   */

  module.exports = function getActual(obj, args) {
    return args.length > 4 ? args[4] : obj._obj;
  };

  },{}],17:[function(require,module,exports){
  /*!
   * Chai - getEnumerableProperties utility
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /**
   * ### .getEnumerableProperties(object)
   *
   * This allows the retrieval of enumerable property names of an object,
   * inherited or not.
   *
   * @param {Object} object
   * @returns {Array}
   * @namespace Utils
   * @name getEnumerableProperties
   * @api public
   */

  module.exports = function getEnumerableProperties(object) {
    var result = [];
    for (var name in object) {
      result.push(name);
    }
    return result;
  };

  },{}],18:[function(require,module,exports){
  /*!
   * Chai - message composition utility
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /*!
   * Module dependancies
   */

  var flag = require('./flag')
    , getActual = require('./getActual')
    , inspect = require('./inspect')
    , objDisplay = require('./objDisplay');

  /**
   * ### .getMessage(object, message, negateMessage)
   *
   * Construct the error message based on flags
   * and template tags. Template tags will return
   * a stringified inspection of the object referenced.
   *
   * Message template tags:
   * - `#{this}` current asserted object
   * - `#{act}` actual value
   * - `#{exp}` expected value
   *
   * @param {Object} object (constructed Assertion)
   * @param {Arguments} chai.Assertion.prototype.assert arguments
   * @namespace Utils
   * @name getMessage
   * @api public
   */

  module.exports = function getMessage(obj, args) {
    var negate = flag(obj, 'negate')
      , val = flag(obj, 'object')
      , expected = args[3]
      , actual = getActual(obj, args)
      , msg = negate ? args[2] : args[1]
      , flagMsg = flag(obj, 'message');

    if(typeof msg === "function") msg = msg();
    msg = msg || '';
    msg = msg
      .replace(/#\{this\}/g, function () { return objDisplay(val); })
      .replace(/#\{act\}/g, function () { return objDisplay(actual); })
      .replace(/#\{exp\}/g, function () { return objDisplay(expected); });

    return flagMsg ? flagMsg + ': ' + msg : msg;
  };

  },{"./flag":15,"./getActual":16,"./inspect":23,"./objDisplay":26}],19:[function(require,module,exports){
  /*!
   * Chai - getOwnEnumerableProperties utility
   * Copyright(c) 2011-2016 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /*!
   * Module dependancies
   */

  var getOwnEnumerablePropertySymbols = require('./getOwnEnumerablePropertySymbols');

  /**
   * ### .getOwnEnumerableProperties(object)
   *
   * This allows the retrieval of directly-owned enumerable property names and
   * symbols of an object. This function is necessary because Object.keys only
   * returns enumerable property names, not enumerable property symbols.
   *
   * @param {Object} object
   * @returns {Array}
   * @namespace Utils
   * @name getOwnEnumerableProperties
   * @api public
   */

  module.exports = function getOwnEnumerableProperties(obj) {
    return Object.keys(obj).concat(getOwnEnumerablePropertySymbols(obj));
  };

  },{"./getOwnEnumerablePropertySymbols":20}],20:[function(require,module,exports){
  /*!
   * Chai - getOwnEnumerablePropertySymbols utility
   * Copyright(c) 2011-2016 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /**
   * ### .getOwnEnumerablePropertySymbols(object)
   *
   * This allows the retrieval of directly-owned enumerable property symbols of an
   * object. This function is necessary because Object.getOwnPropertySymbols
   * returns both enumerable and non-enumerable property symbols.
   *
   * @param {Object} object
   * @returns {Array}
   * @namespace Utils
   * @name getOwnEnumerablePropertySymbols
   * @api public
   */

  module.exports = function getOwnEnumerablePropertySymbols(obj) {
    if (typeof Object.getOwnPropertySymbols !== 'function') return [];

    return Object.getOwnPropertySymbols(obj).filter(function (sym) {
      return Object.getOwnPropertyDescriptor(obj, sym).enumerable;
    });
  };

  },{}],21:[function(require,module,exports){
  /*!
   * Chai - getProperties utility
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /**
   * ### .getProperties(object)
   *
   * This allows the retrieval of property names of an object, enumerable or not,
   * inherited or not.
   *
   * @param {Object} object
   * @returns {Array}
   * @namespace Utils
   * @name getProperties
   * @api public
   */

  module.exports = function getProperties(object) {
    var result = Object.getOwnPropertyNames(object);

    function addProperty(property) {
      if (result.indexOf(property) === -1) {
        result.push(property);
      }
    }

    var proto = Object.getPrototypeOf(object);
    while (proto !== null) {
      Object.getOwnPropertyNames(proto).forEach(addProperty);
      proto = Object.getPrototypeOf(proto);
    }

    return result;
  };

  },{}],22:[function(require,module,exports){
  /*!
   * chai
   * Copyright(c) 2011 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /*!
   * Dependencies that are used for multiple exports are required here only once
   */

  var pathval = require('pathval');

  /*!
   * test utility
   */

  exports.test = require('./test');

  /*!
   * type utility
   */

  exports.type = require('type-detect');

  /*!
   * expectTypes utility
   */
  exports.expectTypes = require('./expectTypes');

  /*!
   * message utility
   */

  exports.getMessage = require('./getMessage');

  /*!
   * actual utility
   */

  exports.getActual = require('./getActual');

  /*!
   * Inspect util
   */

  exports.inspect = require('./inspect');

  /*!
   * Object Display util
   */

  exports.objDisplay = require('./objDisplay');

  /*!
   * Flag utility
   */

  exports.flag = require('./flag');

  /*!
   * Flag transferring utility
   */

  exports.transferFlags = require('./transferFlags');

  /*!
   * Deep equal utility
   */

  exports.eql = require('deep-eql');

  /*!
   * Deep path info
   */

  exports.getPathInfo = pathval.getPathInfo;

  /*!
   * Check if a property exists
   */

  exports.hasProperty = pathval.hasProperty;

  /*!
   * Function name
   */

  exports.getName = require('get-func-name');

  /*!
   * add Property
   */

  exports.addProperty = require('./addProperty');

  /*!
   * add Method
   */

  exports.addMethod = require('./addMethod');

  /*!
   * overwrite Property
   */

  exports.overwriteProperty = require('./overwriteProperty');

  /*!
   * overwrite Method
   */

  exports.overwriteMethod = require('./overwriteMethod');

  /*!
   * Add a chainable method
   */

  exports.addChainableMethod = require('./addChainableMethod');

  /*!
   * Overwrite chainable method
   */

  exports.overwriteChainableMethod = require('./overwriteChainableMethod');

  /*!
   * Compare by inspect method
   */

  exports.compareByInspect = require('./compareByInspect');

  /*!
   * Get own enumerable property symbols method
   */

  exports.getOwnEnumerablePropertySymbols = require('./getOwnEnumerablePropertySymbols');

  /*!
   * Get own enumerable properties method
   */

  exports.getOwnEnumerableProperties = require('./getOwnEnumerableProperties');

  /*!
   * Checks error against a given set of criteria
   */

  exports.checkError = require('check-error');

  /*!
   * Proxify util
   */

  exports.proxify = require('./proxify');

  /*!
   * addLengthGuard util
   */

  exports.addLengthGuard = require('./addLengthGuard');

  /*!
   * isProxyEnabled helper
   */

  exports.isProxyEnabled = require('./isProxyEnabled');

  /*!
   * isNaN method
   */

  exports.isNaN = require('./isNaN');

  },{"./addChainableMethod":9,"./addLengthGuard":10,"./addMethod":11,"./addProperty":12,"./compareByInspect":13,"./expectTypes":14,"./flag":15,"./getActual":16,"./getMessage":18,"./getOwnEnumerableProperties":19,"./getOwnEnumerablePropertySymbols":20,"./inspect":23,"./isNaN":24,"./isProxyEnabled":25,"./objDisplay":26,"./overwriteChainableMethod":27,"./overwriteMethod":28,"./overwriteProperty":29,"./proxify":30,"./test":31,"./transferFlags":32,"check-error":34,"deep-eql":35,"get-func-name":36,"pathval":37,"type-detect":38}],23:[function(require,module,exports){
  // This is (almost) directly from Node.js utils
  // https://github.com/joyent/node/blob/f8c335d0caf47f16d31413f89aa28eda3878e3aa/lib/util.js

  var getName = require('get-func-name');
  var getProperties = require('./getProperties');
  var getEnumerableProperties = require('./getEnumerableProperties');
  var config = require('../config');

  module.exports = inspect;

  /**
   * ### .inspect(obj, [showHidden], [depth], [colors])
   *
   * Echoes the value of a value. Tries to print the value out
   * in the best way possible given the different types.
   *
   * @param {Object} obj The object to print out.
   * @param {Boolean} showHidden Flag that shows hidden (not enumerable)
   *    properties of objects. Default is false.
   * @param {Number} depth Depth in which to descend in object. Default is 2.
   * @param {Boolean} colors Flag to turn on ANSI escape codes to color the
   *    output. Default is false (no coloring).
   * @namespace Utils
   * @name inspect
   */
  function inspect(obj, showHidden, depth, colors) {
    var ctx = {
      showHidden: showHidden,
      seen: [],
      stylize: function (str) { return str; }
    };
    return formatValue(ctx, obj, (typeof depth === 'undefined' ? 2 : depth));
  }

  // Returns true if object is a DOM element.
  var isDOMElement = function (object) {
    if (typeof HTMLElement === 'object') {
      return object instanceof HTMLElement;
    } else {
      return object &&
        typeof object === 'object' &&
        'nodeType' in object &&
        object.nodeType === 1 &&
        typeof object.nodeName === 'string';
    }
  };

  function formatValue(ctx, value, recurseTimes) {
    // Provide a hook for user-specified inspect functions.
    // Check that value is an object with an inspect function on it
    if (value && typeof value.inspect === 'function' &&
        // Filter out the util module, it's inspect function is special
        value.inspect !== exports.inspect &&
        // Also filter out any prototype objects using the circular check.
        !(value.constructor && value.constructor.prototype === value)) {
      var ret = value.inspect(recurseTimes, ctx);
      if (typeof ret !== 'string') {
        ret = formatValue(ctx, ret, recurseTimes);
      }
      return ret;
    }

    // Primitive types cannot have properties
    var primitive = formatPrimitive(ctx, value);
    if (primitive) {
      return primitive;
    }

    // If this is a DOM element, try to get the outer HTML.
    if (isDOMElement(value)) {
      if ('outerHTML' in value) {
        return value.outerHTML;
        // This value does not have an outerHTML attribute,
        //   it could still be an XML element
      } else {
        // Attempt to serialize it
        try {
          if (document.xmlVersion) {
            var xmlSerializer = new XMLSerializer();
            return xmlSerializer.serializeToString(value);
          } else {
            // Firefox 11- do not support outerHTML
            //   It does, however, support innerHTML
            //   Use the following to render the element
            var ns = "http://www.w3.org/1999/xhtml";
            var container = document.createElementNS(ns, '_');

            container.appendChild(value.cloneNode(false));
            var html = container.innerHTML
              .replace('><', '>' + value.innerHTML + '<');
            container.innerHTML = '';
            return html;
          }
        } catch (err) {
          // This could be a non-native DOM implementation,
          //   continue with the normal flow:
          //   printing the element as if it is an object.
        }
      }
    }

    // Look up the keys of the object.
    var visibleKeys = getEnumerableProperties(value);
    var keys = ctx.showHidden ? getProperties(value) : visibleKeys;

    var name, nameSuffix;

    // Some type of object without properties can be shortcutted.
    // In IE, errors have a single `stack` property, or if they are vanilla `Error`,
    // a `stack` plus `description` property; ignore those for consistency.
    if (keys.length === 0 || (isError(value) && (
        (keys.length === 1 && keys[0] === 'stack') ||
        (keys.length === 2 && keys[0] === 'description' && keys[1] === 'stack')
       ))) {
      if (typeof value === 'function') {
        name = getName(value);
        nameSuffix = name ? ': ' + name : '';
        return ctx.stylize('[Function' + nameSuffix + ']', 'special');
      }
      if (isRegExp(value)) {
        return ctx.stylize(RegExp.prototype.toString.call(value), 'regexp');
      }
      if (isDate(value)) {
        return ctx.stylize(Date.prototype.toUTCString.call(value), 'date');
      }
      if (isError(value)) {
        return formatError(value);
      }
    }

    var base = ''
      , array = false
      , typedArray = false
      , braces = ['{', '}'];

    if (isTypedArray(value)) {
      typedArray = true;
      braces = ['[', ']'];
    }

    // Make Array say that they are Array
    if (isArray(value)) {
      array = true;
      braces = ['[', ']'];
    }

    // Make functions say that they are functions
    if (typeof value === 'function') {
      name = getName(value);
      nameSuffix = name ? ': ' + name : '';
      base = ' [Function' + nameSuffix + ']';
    }

    // Make RegExps say that they are RegExps
    if (isRegExp(value)) {
      base = ' ' + RegExp.prototype.toString.call(value);
    }

    // Make dates with properties first say the date
    if (isDate(value)) {
      base = ' ' + Date.prototype.toUTCString.call(value);
    }

    // Make error with message first say the error
    if (isError(value)) {
      return formatError(value);
    }

    if (keys.length === 0 && (!array || value.length == 0)) {
      return braces[0] + base + braces[1];
    }

    if (recurseTimes < 0) {
      if (isRegExp(value)) {
        return ctx.stylize(RegExp.prototype.toString.call(value), 'regexp');
      } else {
        return ctx.stylize('[Object]', 'special');
      }
    }

    ctx.seen.push(value);

    var output;
    if (array) {
      output = formatArray(ctx, value, recurseTimes, visibleKeys, keys);
    } else if (typedArray) {
      return formatTypedArray(value);
    } else {
      output = keys.map(function(key) {
        return formatProperty(ctx, value, recurseTimes, visibleKeys, key, array);
      });
    }

    ctx.seen.pop();

    return reduceToSingleString(output, base, braces);
  }


  function formatPrimitive(ctx, value) {
    switch (typeof value) {
      case 'undefined':
        return ctx.stylize('undefined', 'undefined');

      case 'string':
        var simple = '\'' + JSON.stringify(value).replace(/^"|"$/g, '')
                                                 .replace(/'/g, "\\'")
                                                 .replace(/\\"/g, '"') + '\'';
        return ctx.stylize(simple, 'string');

      case 'number':
        if (value === 0 && (1/value) === -Infinity) {
          return ctx.stylize('-0', 'number');
        }
        return ctx.stylize('' + value, 'number');

      case 'boolean':
        return ctx.stylize('' + value, 'boolean');

      case 'symbol':
        return ctx.stylize(value.toString(), 'symbol');
    }
    // For some reason typeof null is "object", so special case here.
    if (value === null) {
      return ctx.stylize('null', 'null');
    }
  }


  function formatError(value) {
    return '[' + Error.prototype.toString.call(value) + ']';
  }


  function formatArray(ctx, value, recurseTimes, visibleKeys, keys) {
    var output = [];
    for (var i = 0, l = value.length; i < l; ++i) {
      if (Object.prototype.hasOwnProperty.call(value, String(i))) {
        output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
            String(i), true));
      } else {
        output.push('');
      }
    }

    keys.forEach(function(key) {
      if (!key.match(/^\d+$/)) {
        output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
            key, true));
      }
    });
    return output;
  }

  function formatTypedArray(value) {
    var str = '[ ';

    for (var i = 0; i < value.length; ++i) {
      if (str.length >= config.truncateThreshold - 7) {
        str += '...';
        break;
      }
      str += value[i] + ', ';
    }
    str += ' ]';

    // Removing trailing `, ` if the array was not truncated
    if (str.indexOf(',  ]') !== -1) {
      str = str.replace(',  ]', ' ]');
    }

    return str;
  }

  function formatProperty(ctx, value, recurseTimes, visibleKeys, key, array) {
    var name;
    var propDescriptor = Object.getOwnPropertyDescriptor(value, key);
    var str;

    if (propDescriptor) {
      if (propDescriptor.get) {
        if (propDescriptor.set) {
          str = ctx.stylize('[Getter/Setter]', 'special');
        } else {
          str = ctx.stylize('[Getter]', 'special');
        }
      } else {
        if (propDescriptor.set) {
          str = ctx.stylize('[Setter]', 'special');
        }
      }
    }
    if (visibleKeys.indexOf(key) < 0) {
      name = '[' + key + ']';
    }
    if (!str) {
      if (ctx.seen.indexOf(value[key]) < 0) {
        if (recurseTimes === null) {
          str = formatValue(ctx, value[key], null);
        } else {
          str = formatValue(ctx, value[key], recurseTimes - 1);
        }
        if (str.indexOf('\n') > -1) {
          if (array) {
            str = str.split('\n').map(function(line) {
              return '  ' + line;
            }).join('\n').substr(2);
          } else {
            str = '\n' + str.split('\n').map(function(line) {
              return '   ' + line;
            }).join('\n');
          }
        }
      } else {
        str = ctx.stylize('[Circular]', 'special');
      }
    }
    if (typeof name === 'undefined') {
      if (array && key.match(/^\d+$/)) {
        return str;
      }
      name = JSON.stringify('' + key);
      if (name.match(/^"([a-zA-Z_][a-zA-Z_0-9]*)"$/)) {
        name = name.substr(1, name.length - 2);
        name = ctx.stylize(name, 'name');
      } else {
        name = name.replace(/'/g, "\\'")
                   .replace(/\\"/g, '"')
                   .replace(/(^"|"$)/g, "'");
        name = ctx.stylize(name, 'string');
      }
    }

    return name + ': ' + str;
  }


  function reduceToSingleString(output, base, braces) {
    var numLinesEst = 0;
    var length = output.reduce(function(prev, cur) {
      numLinesEst++;
      if (cur.indexOf('\n') >= 0) numLinesEst++;
      return prev + cur.length + 1;
    }, 0);

    if (length > 60) {
      return braces[0] +
             (base === '' ? '' : base + '\n ') +
             ' ' +
             output.join(',\n  ') +
             ' ' +
             braces[1];
    }

    return braces[0] + base + ' ' + output.join(', ') + ' ' + braces[1];
  }

  function isTypedArray(ar) {
    // Unfortunately there's no way to check if an object is a TypedArray
    // We have to check if it's one of these types
    return (typeof ar === 'object' && /\w+Array]$/.test(objectToString(ar)));
  }

  function isArray(ar) {
    return Array.isArray(ar) ||
           (typeof ar === 'object' && objectToString(ar) === '[object Array]');
  }

  function isRegExp(re) {
    return typeof re === 'object' && objectToString(re) === '[object RegExp]';
  }

  function isDate(d) {
    return typeof d === 'object' && objectToString(d) === '[object Date]';
  }

  function isError(e) {
    return typeof e === 'object' && objectToString(e) === '[object Error]';
  }

  function objectToString(o) {
    return Object.prototype.toString.call(o);
  }

  },{"../config":4,"./getEnumerableProperties":17,"./getProperties":21,"get-func-name":36}],24:[function(require,module,exports){
  /*!
   * Chai - isNaN utility
   * Copyright(c) 2012-2015 Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
   * MIT Licensed
   */

  /**
   * ### .isNaN(value)
   *
   * Checks if the given value is NaN or not.
   *
   *     utils.isNaN(NaN); // true
   *
   * @param {Value} The value which has to be checked if it is NaN
   * @name isNaN
   * @api private
   */

  function isNaN(value) {
    // Refer http://www.ecma-international.org/ecma-262/6.0/#sec-isnan-number
    // section's NOTE.
    return value !== value;
  }

  // If ECMAScript 6's Number.isNaN is present, prefer that.
  module.exports = Number.isNaN || isNaN;

  },{}],25:[function(require,module,exports){
  var config = require('../config');

  /*!
   * Chai - isProxyEnabled helper
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /**
   * ### .isProxyEnabled()
   *
   * Helper function to check if Chai's proxy protection feature is enabled. If
   * proxies are unsupported or disabled via the user's Chai config, then return
   * false. Otherwise, return true.
   *
   * @namespace Utils
   * @name isProxyEnabled
   */

  module.exports = function isProxyEnabled() {
    return config.useProxy &&
      typeof Proxy !== 'undefined' &&
      typeof Reflect !== 'undefined';
  };

  },{"../config":4}],26:[function(require,module,exports){
  /*!
   * Chai - flag utility
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /*!
   * Module dependancies
   */

  var inspect = require('./inspect');
  var config = require('../config');

  /**
   * ### .objDisplay(object)
   *
   * Determines if an object or an array matches
   * criteria to be inspected in-line for error
   * messages or should be truncated.
   *
   * @param {Mixed} javascript object to inspect
   * @name objDisplay
   * @namespace Utils
   * @api public
   */

  module.exports = function objDisplay(obj) {
    var str = inspect(obj)
      , type = Object.prototype.toString.call(obj);

    if (config.truncateThreshold && str.length >= config.truncateThreshold) {
      if (type === '[object Function]') {
        return !obj.name || obj.name === ''
          ? '[Function]'
          : '[Function: ' + obj.name + ']';
      } else if (type === '[object Array]') {
        return '[ Array(' + obj.length + ') ]';
      } else if (type === '[object Object]') {
        var keys = Object.keys(obj)
          , kstr = keys.length > 2
            ? keys.splice(0, 2).join(', ') + ', ...'
            : keys.join(', ');
        return '{ Object (' + kstr + ') }';
      } else {
        return str;
      }
    } else {
      return str;
    }
  };

  },{"../config":4,"./inspect":23}],27:[function(require,module,exports){
  /*!
   * Chai - overwriteChainableMethod utility
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  var chai = require('../../chai');
  var transferFlags = require('./transferFlags');

  /**
   * ### .overwriteChainableMethod(ctx, name, method, chainingBehavior)
   *
   * Overwites an already existing chainable method
   * and provides access to the previous function or
   * property.  Must return functions to be used for
   * name.
   *
   *     utils.overwriteChainableMethod(chai.Assertion.prototype, 'lengthOf',
   *       function (_super) {
   *       }
   *     , function (_super) {
   *       }
   *     );
   *
   * Can also be accessed directly from `chai.Assertion`.
   *
   *     chai.Assertion.overwriteChainableMethod('foo', fn, fn);
   *
   * Then can be used as any other assertion.
   *
   *     expect(myFoo).to.have.lengthOf(3);
   *     expect(myFoo).to.have.lengthOf.above(3);
   *
   * @param {Object} ctx object whose method / property is to be overwritten
   * @param {String} name of method / property to overwrite
   * @param {Function} method function that returns a function to be used for name
   * @param {Function} chainingBehavior function that returns a function to be used for property
   * @namespace Utils
   * @name overwriteChainableMethod
   * @api public
   */

  module.exports = function overwriteChainableMethod(ctx, name, method, chainingBehavior) {
    var chainableBehavior = ctx.__methods[name];

    var _chainingBehavior = chainableBehavior.chainingBehavior;
    chainableBehavior.chainingBehavior = function overwritingChainableMethodGetter() {
      var result = chainingBehavior(_chainingBehavior).call(this);
      if (result !== undefined) {
        return result;
      }

      var newAssertion = new chai.Assertion();
      transferFlags(this, newAssertion);
      return newAssertion;
    };

    var _method = chainableBehavior.method;
    chainableBehavior.method = function overwritingChainableMethodWrapper() {
      var result = method(_method).apply(this, arguments);
      if (result !== undefined) {
        return result;
      }

      var newAssertion = new chai.Assertion();
      transferFlags(this, newAssertion);
      return newAssertion;
    };
  };

  },{"../../chai":2,"./transferFlags":32}],28:[function(require,module,exports){
  /*!
   * Chai - overwriteMethod utility
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  var addLengthGuard = require('./addLengthGuard');
  var chai = require('../../chai');
  var flag = require('./flag');
  var proxify = require('./proxify');
  var transferFlags = require('./transferFlags');

  /**
   * ### .overwriteMethod(ctx, name, fn)
   *
   * Overwites an already existing method and provides
   * access to previous function. Must return function
   * to be used for name.
   *
   *     utils.overwriteMethod(chai.Assertion.prototype, 'equal', function (_super) {
   *       return function (str) {
   *         var obj = utils.flag(this, 'object');
   *         if (obj instanceof Foo) {
   *           new chai.Assertion(obj.value).to.equal(str);
   *         } else {
   *           _super.apply(this, arguments);
   *         }
   *       }
   *     });
   *
   * Can also be accessed directly from `chai.Assertion`.
   *
   *     chai.Assertion.overwriteMethod('foo', fn);
   *
   * Then can be used as any other assertion.
   *
   *     expect(myFoo).to.equal('bar');
   *
   * @param {Object} ctx object whose method is to be overwritten
   * @param {String} name of method to overwrite
   * @param {Function} method function that returns a function to be used for name
   * @namespace Utils
   * @name overwriteMethod
   * @api public
   */

  module.exports = function overwriteMethod(ctx, name, method) {
    var _method = ctx[name]
      , _super = function () {
        throw new Error(name + ' is not a function');
      };

    if (_method && 'function' === typeof _method)
      _super = _method;

    var overwritingMethodWrapper = function () {
      // Setting the `ssfi` flag to `overwritingMethodWrapper` causes this
      // function to be the starting point for removing implementation frames from
      // the stack trace of a failed assertion.
      //
      // However, we only want to use this function as the starting point if the
      // `lockSsfi` flag isn't set.
      //
      // If the `lockSsfi` flag is set, then either this assertion has been
      // overwritten by another assertion, or this assertion is being invoked from
      // inside of another assertion. In the first case, the `ssfi` flag has
      // already been set by the overwriting assertion. In the second case, the
      // `ssfi` flag has already been set by the outer assertion.
      if (!flag(this, 'lockSsfi')) {
        flag(this, 'ssfi', overwritingMethodWrapper);
      }

      // Setting the `lockSsfi` flag to `true` prevents the overwritten assertion
      // from changing the `ssfi` flag. By this point, the `ssfi` flag is already
      // set to the correct starting point for this assertion.
      var origLockSsfi = flag(this, 'lockSsfi');
      flag(this, 'lockSsfi', true);
      var result = method(_super).apply(this, arguments);
      flag(this, 'lockSsfi', origLockSsfi);

      if (result !== undefined) {
        return result;
      }

      var newAssertion = new chai.Assertion();
      transferFlags(this, newAssertion);
      return newAssertion;
    }

    addLengthGuard(overwritingMethodWrapper, name, false);
    ctx[name] = proxify(overwritingMethodWrapper, name);
  };

  },{"../../chai":2,"./addLengthGuard":10,"./flag":15,"./proxify":30,"./transferFlags":32}],29:[function(require,module,exports){
  /*!
   * Chai - overwriteProperty utility
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  var chai = require('../../chai');
  var flag = require('./flag');
  var isProxyEnabled = require('./isProxyEnabled');
  var transferFlags = require('./transferFlags');

  /**
   * ### .overwriteProperty(ctx, name, fn)
   *
   * Overwites an already existing property getter and provides
   * access to previous value. Must return function to use as getter.
   *
   *     utils.overwriteProperty(chai.Assertion.prototype, 'ok', function (_super) {
   *       return function () {
   *         var obj = utils.flag(this, 'object');
   *         if (obj instanceof Foo) {
   *           new chai.Assertion(obj.name).to.equal('bar');
   *         } else {
   *           _super.call(this);
   *         }
   *       }
   *     });
   *
   *
   * Can also be accessed directly from `chai.Assertion`.
   *
   *     chai.Assertion.overwriteProperty('foo', fn);
   *
   * Then can be used as any other assertion.
   *
   *     expect(myFoo).to.be.ok;
   *
   * @param {Object} ctx object whose property is to be overwritten
   * @param {String} name of property to overwrite
   * @param {Function} getter function that returns a getter function to be used for name
   * @namespace Utils
   * @name overwriteProperty
   * @api public
   */

  module.exports = function overwriteProperty(ctx, name, getter) {
    var _get = Object.getOwnPropertyDescriptor(ctx, name)
      , _super = function () {};

    if (_get && 'function' === typeof _get.get)
      _super = _get.get

    Object.defineProperty(ctx, name,
      { get: function overwritingPropertyGetter() {
          // Setting the `ssfi` flag to `overwritingPropertyGetter` causes this
          // function to be the starting point for removing implementation frames
          // from the stack trace of a failed assertion.
          //
          // However, we only want to use this function as the starting point if
          // the `lockSsfi` flag isn't set and proxy protection is disabled.
          //
          // If the `lockSsfi` flag is set, then either this assertion has been
          // overwritten by another assertion, or this assertion is being invoked
          // from inside of another assertion. In the first case, the `ssfi` flag
          // has already been set by the overwriting assertion. In the second
          // case, the `ssfi` flag has already been set by the outer assertion.
          //
          // If proxy protection is enabled, then the `ssfi` flag has already been
          // set by the proxy getter.
          if (!isProxyEnabled() && !flag(this, 'lockSsfi')) {
            flag(this, 'ssfi', overwritingPropertyGetter);
          }

          // Setting the `lockSsfi` flag to `true` prevents the overwritten
          // assertion from changing the `ssfi` flag. By this point, the `ssfi`
          // flag is already set to the correct starting point for this assertion.
          var origLockSsfi = flag(this, 'lockSsfi');
          flag(this, 'lockSsfi', true);
          var result = getter(_super).call(this);
          flag(this, 'lockSsfi', origLockSsfi);

          if (result !== undefined) {
            return result;
          }

          var newAssertion = new chai.Assertion();
          transferFlags(this, newAssertion);
          return newAssertion;
        }
      , configurable: true
    });
  };

  },{"../../chai":2,"./flag":15,"./isProxyEnabled":25,"./transferFlags":32}],30:[function(require,module,exports){
  var config = require('../config');
  var flag = require('./flag');
  var getProperties = require('./getProperties');
  var isProxyEnabled = require('./isProxyEnabled');

  /*!
   * Chai - proxify utility
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /**
   * ### .proxify(object)
   *
   * Return a proxy of given object that throws an error when a non-existent
   * property is read. By default, the root cause is assumed to be a misspelled
   * property, and thus an attempt is made to offer a reasonable suggestion from
   * the list of existing properties. However, if a nonChainableMethodName is
   * provided, then the root cause is instead a failure to invoke a non-chainable
   * method prior to reading the non-existent property.
   *
   * If proxies are unsupported or disabled via the user's Chai config, then
   * return object without modification.
   *
   * @param {Object} obj
   * @param {String} nonChainableMethodName
   * @namespace Utils
   * @name proxify
   */

  var builtins = ['__flags', '__methods', '_obj', 'assert'];

  module.exports = function proxify(obj, nonChainableMethodName) {
    if (!isProxyEnabled()) return obj;

    return new Proxy(obj, {
      get: function proxyGetter(target, property) {
        // This check is here because we should not throw errors on Symbol properties
        // such as `Symbol.toStringTag`.
        // The values for which an error should be thrown can be configured using
        // the `config.proxyExcludedKeys` setting.
        if (typeof property === 'string' &&
            config.proxyExcludedKeys.indexOf(property) === -1 &&
            !Reflect.has(target, property)) {
          // Special message for invalid property access of non-chainable methods.
          if (nonChainableMethodName) {
            throw Error('Invalid Chai property: ' + nonChainableMethodName + '.' +
              property + '. See docs for proper usage of "' +
              nonChainableMethodName + '".');
          }

          var orderedProperties = getProperties(target).filter(function(property) {
            return !Object.prototype.hasOwnProperty(property) &&
              builtins.indexOf(property) === -1;
          }).sort(function(a, b) {
            return stringDistance(property, a) - stringDistance(property, b);
          });

          if (orderedProperties.length &&
              stringDistance(orderedProperties[0], property) < 4) {
            // If the property is reasonably close to an existing Chai property,
            // suggest that property to the user.
            throw Error('Invalid Chai property: ' + property +
              '. Did you mean "' + orderedProperties[0] + '"?');
          } else {
            throw Error('Invalid Chai property: ' + property);
          }
        }

        // Use this proxy getter as the starting point for removing implementation
        // frames from the stack trace of a failed assertion. For property
        // assertions, this prevents the proxy getter from showing up in the stack
        // trace since it's invoked before the property getter. For method and
        // chainable method assertions, this flag will end up getting changed to
        // the method wrapper, which is good since this frame will no longer be in
        // the stack once the method is invoked. Note that Chai builtin assertion
        // properties such as `__flags` are skipped since this is only meant to
        // capture the starting point of an assertion. This step is also skipped
        // if the `lockSsfi` flag is set, thus indicating that this assertion is
        // being called from within another assertion. In that case, the `ssfi`
        // flag is already set to the outer assertion's starting point.
        if (builtins.indexOf(property) === -1 && !flag(target, 'lockSsfi')) {
          flag(target, 'ssfi', proxyGetter);
        }

        return Reflect.get(target, property);
      }
    });
  };

  /**
   * # stringDistance(strA, strB)
   * Return the Levenshtein distance between two strings.
   * @param {string} strA
   * @param {string} strB
   * @return {number} the string distance between strA and strB
   * @api private
   */

  function stringDistance(strA, strB, memo) {
    if (!memo) {
      // `memo` is a two-dimensional array containing a cache of distances
      // memo[i][j] is the distance between strA.slice(0, i) and
      // strB.slice(0, j).
      memo = [];
      for (var i = 0; i <= strA.length; i++) {
        memo[i] = [];
      }
    }

    if (!memo[strA.length] || !memo[strA.length][strB.length]) {
      if (strA.length === 0 || strB.length === 0) {
        memo[strA.length][strB.length] = Math.max(strA.length, strB.length);
      } else {
        memo[strA.length][strB.length] = Math.min(
          stringDistance(strA.slice(0, -1), strB, memo) + 1,
          stringDistance(strA, strB.slice(0, -1), memo) + 1,
          stringDistance(strA.slice(0, -1), strB.slice(0, -1), memo) +
            (strA.slice(-1) === strB.slice(-1) ? 0 : 1)
        );
      }
    }

    return memo[strA.length][strB.length];
  }

  },{"../config":4,"./flag":15,"./getProperties":21,"./isProxyEnabled":25}],31:[function(require,module,exports){
  /*!
   * Chai - test utility
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /*!
   * Module dependancies
   */

  var flag = require('./flag');

  /**
   * ### .test(object, expression)
   *
   * Test and object for expression.
   *
   * @param {Object} object (constructed Assertion)
   * @param {Arguments} chai.Assertion.prototype.assert arguments
   * @namespace Utils
   * @name test
   */

  module.exports = function test(obj, args) {
    var negate = flag(obj, 'negate')
      , expr = args[0];
    return negate ? !expr : expr;
  };

  },{"./flag":15}],32:[function(require,module,exports){
  /*!
   * Chai - transferFlags utility
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /**
   * ### .transferFlags(assertion, object, includeAll = true)
   *
   * Transfer all the flags for `assertion` to `object`. If
   * `includeAll` is set to `false`, then the base Chai
   * assertion flags (namely `object`, `ssfi`, `lockSsfi`,
   * and `message`) will not be transferred.
   *
   *
   *     var newAssertion = new Assertion();
   *     utils.transferFlags(assertion, newAssertion);
   *
   *     var anotherAsseriton = new Assertion(myObj);
   *     utils.transferFlags(assertion, anotherAssertion, false);
   *
   * @param {Assertion} assertion the assertion to transfer the flags from
   * @param {Object} object the object to transfer the flags to; usually a new assertion
   * @param {Boolean} includeAll
   * @namespace Utils
   * @name transferFlags
   * @api private
   */

  module.exports = function transferFlags(assertion, object, includeAll) {
    var flags = assertion.__flags || (assertion.__flags = Object.create(null));

    if (!object.__flags) {
      object.__flags = Object.create(null);
    }

    includeAll = arguments.length === 3 ? includeAll : true;

    for (var flag in flags) {
      if (includeAll ||
          (flag !== 'object' && flag !== 'ssfi' && flag !== 'lockSsfi' && flag != 'message')) {
        object.__flags[flag] = flags[flag];
      }
    }
  };

  },{}],33:[function(require,module,exports){
  /*!
   * assertion-error
   * Copyright(c) 2013 Jake Luer <jake@qualiancy.com>
   * MIT Licensed
   */

  /*!
   * Return a function that will copy properties from
   * one object to another excluding any originally
   * listed. Returned function will create a new `{}`.
   *
   * @param {String} excluded properties ...
   * @return {Function}
   */

  function exclude () {
    var excludes = [].slice.call(arguments);

    function excludeProps (res, obj) {
      Object.keys(obj).forEach(function (key) {
        if (!~excludes.indexOf(key)) res[key] = obj[key];
      });
    }

    return function extendExclude () {
      var args = [].slice.call(arguments)
        , i = 0
        , res = {};

      for (; i < args.length; i++) {
        excludeProps(res, args[i]);
      }

      return res;
    };
  };

  /*!
   * Primary Exports
   */

  module.exports = AssertionError;

  /**
   * ### AssertionError
   *
   * An extension of the JavaScript `Error` constructor for
   * assertion and validation scenarios.
   *
   * @param {String} message
   * @param {Object} properties to include (optional)
   * @param {callee} start stack function (optional)
   */

  function AssertionError (message, _props, ssf) {
    var extend = exclude('name', 'message', 'stack', 'constructor', 'toJSON')
      , props = extend(_props || {});

    // default values
    this.message = message || 'Unspecified AssertionError';
    this.showDiff = false;

    // copy from properties
    for (var key in props) {
      this[key] = props[key];
    }

    // capture stack trace
    ssf = ssf || arguments.callee;
    if (ssf && Error.captureStackTrace) {
      Error.captureStackTrace(this, ssf);
    } else {
      try {
        throw new Error();
      } catch(e) {
        this.stack = e.stack;
      }
    }
  }

  /*!
   * Inherit from Error.prototype
   */

  AssertionError.prototype = Object.create(Error.prototype);

  /*!
   * Statically set name
   */

  AssertionError.prototype.name = 'AssertionError';

  /*!
   * Ensure correct constructor
   */

  AssertionError.prototype.constructor = AssertionError;

  /**
   * Allow errors to be converted to JSON for static transfer.
   *
   * @param {Boolean} include stack (default: `true`)
   * @return {Object} object that can be `JSON.stringify`
   */

  AssertionError.prototype.toJSON = function (stack) {
    var extend = exclude('constructor', 'toJSON', 'stack')
      , props = extend({ name: this.name }, this);

    // include stack if exists and not turned off
    if (false !== stack && this.stack) {
      props.stack = this.stack;
    }

    return props;
  };

  },{}],34:[function(require,module,exports){
  'use strict';

  /* !
   * Chai - checkError utility
   * Copyright(c) 2012-2016 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /**
   * ### .checkError
   *
   * Checks that an error conforms to a given set of criteria and/or retrieves information about it.
   *
   * @api public
   */

  /**
   * ### .compatibleInstance(thrown, errorLike)
   *
   * Checks if two instances are compatible (strict equal).
   * Returns false if errorLike is not an instance of Error, because instances
   * can only be compatible if they're both error instances.
   *
   * @name compatibleInstance
   * @param {Error} thrown error
   * @param {Error|ErrorConstructor} errorLike object to compare against
   * @namespace Utils
   * @api public
   */

  function compatibleInstance(thrown, errorLike) {
    return errorLike instanceof Error && thrown === errorLike;
  }

  /**
   * ### .compatibleConstructor(thrown, errorLike)
   *
   * Checks if two constructors are compatible.
   * This function can receive either an error constructor or
   * an error instance as the `errorLike` argument.
   * Constructors are compatible if they're the same or if one is
   * an instance of another.
   *
   * @name compatibleConstructor
   * @param {Error} thrown error
   * @param {Error|ErrorConstructor} errorLike object to compare against
   * @namespace Utils
   * @api public
   */

  function compatibleConstructor(thrown, errorLike) {
    if (errorLike instanceof Error) {
      // If `errorLike` is an instance of any error we compare their constructors
      return thrown.constructor === errorLike.constructor || thrown instanceof errorLike.constructor;
    } else if (errorLike.prototype instanceof Error || errorLike === Error) {
      // If `errorLike` is a constructor that inherits from Error, we compare `thrown` to `errorLike` directly
      return thrown.constructor === errorLike || thrown instanceof errorLike;
    }

    return false;
  }

  /**
   * ### .compatibleMessage(thrown, errMatcher)
   *
   * Checks if an error's message is compatible with a matcher (String or RegExp).
   * If the message contains the String or passes the RegExp test,
   * it is considered compatible.
   *
   * @name compatibleMessage
   * @param {Error} thrown error
   * @param {String|RegExp} errMatcher to look for into the message
   * @namespace Utils
   * @api public
   */

  function compatibleMessage(thrown, errMatcher) {
    var comparisonString = typeof thrown === 'string' ? thrown : thrown.message;
    if (errMatcher instanceof RegExp) {
      return errMatcher.test(comparisonString);
    } else if (typeof errMatcher === 'string') {
      return comparisonString.indexOf(errMatcher) !== -1; // eslint-disable-line no-magic-numbers
    }

    return false;
  }

  /**
   * ### .getFunctionName(constructorFn)
   *
   * Returns the name of a function.
   * This also includes a polyfill function if `constructorFn.name` is not defined.
   *
   * @name getFunctionName
   * @param {Function} constructorFn
   * @namespace Utils
   * @api private
   */

  var functionNameMatch = /\s*function(?:\s|\s*\/\*[^(?:*\/)]+\*\/\s*)*([^\(\/]+)/;
  function getFunctionName(constructorFn) {
    var name = '';
    if (typeof constructorFn.name === 'undefined') {
      // Here we run a polyfill if constructorFn.name is not defined
      var match = String(constructorFn).match(functionNameMatch);
      if (match) {
        name = match[1];
      }
    } else {
      name = constructorFn.name;
    }

    return name;
  }

  /**
   * ### .getConstructorName(errorLike)
   *
   * Gets the constructor name for an Error instance or constructor itself.
   *
   * @name getConstructorName
   * @param {Error|ErrorConstructor} errorLike
   * @namespace Utils
   * @api public
   */

  function getConstructorName(errorLike) {
    var constructorName = errorLike;
    if (errorLike instanceof Error) {
      constructorName = getFunctionName(errorLike.constructor);
    } else if (typeof errorLike === 'function') {
      // If `err` is not an instance of Error it is an error constructor itself or another function.
      // If we've got a common function we get its name, otherwise we may need to create a new instance
      // of the error just in case it's a poorly-constructed error. Please see chaijs/chai/issues/45 to know more.
      constructorName = getFunctionName(errorLike).trim() ||
          getFunctionName(new errorLike()); // eslint-disable-line new-cap
    }

    return constructorName;
  }

  /**
   * ### .getMessage(errorLike)
   *
   * Gets the error message from an error.
   * If `err` is a String itself, we return it.
   * If the error has no message, we return an empty string.
   *
   * @name getMessage
   * @param {Error|String} errorLike
   * @namespace Utils
   * @api public
   */

  function getMessage(errorLike) {
    var msg = '';
    if (errorLike && errorLike.message) {
      msg = errorLike.message;
    } else if (typeof errorLike === 'string') {
      msg = errorLike;
    }

    return msg;
  }

  module.exports = {
    compatibleInstance: compatibleInstance,
    compatibleConstructor: compatibleConstructor,
    compatibleMessage: compatibleMessage,
    getMessage: getMessage,
    getConstructorName: getConstructorName,
  };

  },{}],35:[function(require,module,exports){
  'use strict';
  /* globals Symbol: false, Uint8Array: false, WeakMap: false */
  /*!
   * deep-eql
   * Copyright(c) 2013 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  var type = require('type-detect');
  function FakeMap() {
    this._key = 'chai/deep-eql__' + Math.random() + Date.now();
  }

  FakeMap.prototype = {
    get: function getMap(key) {
      return key[this._key];
    },
    set: function setMap(key, value) {
      if (!Object.isFrozen(key)) {
        Object.defineProperty(key, this._key, {
          value: value,
          configurable: true,
        });
      }
    },
  };

  var MemoizeMap = typeof WeakMap === 'function' ? WeakMap : FakeMap;
  /*!
   * Check to see if the MemoizeMap has recorded a result of the two operands
   *
   * @param {Mixed} leftHandOperand
   * @param {Mixed} rightHandOperand
   * @param {MemoizeMap} memoizeMap
   * @returns {Boolean|null} result
  */
  function memoizeCompare(leftHandOperand, rightHandOperand, memoizeMap) {
    // Technically, WeakMap keys can *only* be objects, not primitives.
    if (!memoizeMap || isPrimitive(leftHandOperand) || isPrimitive(rightHandOperand)) {
      return null;
    }
    var leftHandMap = memoizeMap.get(leftHandOperand);
    if (leftHandMap) {
      var result = leftHandMap.get(rightHandOperand);
      if (typeof result === 'boolean') {
        return result;
      }
    }
    return null;
  }

  /*!
   * Set the result of the equality into the MemoizeMap
   *
   * @param {Mixed} leftHandOperand
   * @param {Mixed} rightHandOperand
   * @param {MemoizeMap} memoizeMap
   * @param {Boolean} result
  */
  function memoizeSet(leftHandOperand, rightHandOperand, memoizeMap, result) {
    // Technically, WeakMap keys can *only* be objects, not primitives.
    if (!memoizeMap || isPrimitive(leftHandOperand) || isPrimitive(rightHandOperand)) {
      return;
    }
    var leftHandMap = memoizeMap.get(leftHandOperand);
    if (leftHandMap) {
      leftHandMap.set(rightHandOperand, result);
    } else {
      leftHandMap = new MemoizeMap();
      leftHandMap.set(rightHandOperand, result);
      memoizeMap.set(leftHandOperand, leftHandMap);
    }
  }

  /*!
   * Primary Export
   */

  module.exports = deepEqual;
  module.exports.MemoizeMap = MemoizeMap;

  /**
   * Assert deeply nested sameValue equality between two objects of any type.
   *
   * @param {Mixed} leftHandOperand
   * @param {Mixed} rightHandOperand
   * @param {Object} [options] (optional) Additional options
   * @param {Array} [options.comparator] (optional) Override default algorithm, determining custom equality.
   * @param {Array} [options.memoize] (optional) Provide a custom memoization object which will cache the results of
      complex objects for a speed boost. By passing `false` you can disable memoization, but this will cause circular
      references to blow the stack.
   * @return {Boolean} equal match
   */
  function deepEqual(leftHandOperand, rightHandOperand, options) {
    // If we have a comparator, we can't assume anything; so bail to its check first.
    if (options && options.comparator) {
      return extensiveDeepEqual(leftHandOperand, rightHandOperand, options);
    }

    var simpleResult = simpleEqual(leftHandOperand, rightHandOperand);
    if (simpleResult !== null) {
      return simpleResult;
    }

    // Deeper comparisons are pushed through to a larger function
    return extensiveDeepEqual(leftHandOperand, rightHandOperand, options);
  }

  /**
   * Many comparisons can be canceled out early via simple equality or primitive checks.
   * @param {Mixed} leftHandOperand
   * @param {Mixed} rightHandOperand
   * @return {Boolean|null} equal match
   */
  function simpleEqual(leftHandOperand, rightHandOperand) {
    // Equal references (except for Numbers) can be returned early
    if (leftHandOperand === rightHandOperand) {
      // Handle +-0 cases
      return leftHandOperand !== 0 || 1 / leftHandOperand === 1 / rightHandOperand;
    }

    // handle NaN cases
    if (
      leftHandOperand !== leftHandOperand && // eslint-disable-line no-self-compare
      rightHandOperand !== rightHandOperand // eslint-disable-line no-self-compare
    ) {
      return true;
    }

    // Anything that is not an 'object', i.e. symbols, functions, booleans, numbers,
    // strings, and undefined, can be compared by reference.
    if (isPrimitive(leftHandOperand) || isPrimitive(rightHandOperand)) {
      // Easy out b/c it would have passed the first equality check
      return false;
    }
    return null;
  }

  /*!
   * The main logic of the `deepEqual` function.
   *
   * @param {Mixed} leftHandOperand
   * @param {Mixed} rightHandOperand
   * @param {Object} [options] (optional) Additional options
   * @param {Array} [options.comparator] (optional) Override default algorithm, determining custom equality.
   * @param {Array} [options.memoize] (optional) Provide a custom memoization object which will cache the results of
      complex objects for a speed boost. By passing `false` you can disable memoization, but this will cause circular
      references to blow the stack.
   * @return {Boolean} equal match
  */
  function extensiveDeepEqual(leftHandOperand, rightHandOperand, options) {
    options = options || {};
    options.memoize = options.memoize === false ? false : options.memoize || new MemoizeMap();
    var comparator = options && options.comparator;

    // Check if a memoized result exists.
    var memoizeResultLeft = memoizeCompare(leftHandOperand, rightHandOperand, options.memoize);
    if (memoizeResultLeft !== null) {
      return memoizeResultLeft;
    }
    var memoizeResultRight = memoizeCompare(rightHandOperand, leftHandOperand, options.memoize);
    if (memoizeResultRight !== null) {
      return memoizeResultRight;
    }

    // If a comparator is present, use it.
    if (comparator) {
      var comparatorResult = comparator(leftHandOperand, rightHandOperand);
      // Comparators may return null, in which case we want to go back to default behavior.
      if (comparatorResult === false || comparatorResult === true) {
        memoizeSet(leftHandOperand, rightHandOperand, options.memoize, comparatorResult);
        return comparatorResult;
      }
      // To allow comparators to override *any* behavior, we ran them first. Since it didn't decide
      // what to do, we need to make sure to return the basic tests first before we move on.
      var simpleResult = simpleEqual(leftHandOperand, rightHandOperand);
      if (simpleResult !== null) {
        // Don't memoize this, it takes longer to set/retrieve than to just compare.
        return simpleResult;
      }
    }

    var leftHandType = type(leftHandOperand);
    if (leftHandType !== type(rightHandOperand)) {
      memoizeSet(leftHandOperand, rightHandOperand, options.memoize, false);
      return false;
    }

    // Temporarily set the operands in the memoize object to prevent blowing the stack
    memoizeSet(leftHandOperand, rightHandOperand, options.memoize, true);

    var result = extensiveDeepEqualByType(leftHandOperand, rightHandOperand, leftHandType, options);
    memoizeSet(leftHandOperand, rightHandOperand, options.memoize, result);
    return result;
  }

  function extensiveDeepEqualByType(leftHandOperand, rightHandOperand, leftHandType, options) {
    switch (leftHandType) {
      case 'String':
      case 'Number':
      case 'Boolean':
      case 'Date':
        // If these types are their instance types (e.g. `new Number`) then re-deepEqual against their values
        return deepEqual(leftHandOperand.valueOf(), rightHandOperand.valueOf());
      case 'Promise':
      case 'Symbol':
      case 'function':
      case 'WeakMap':
      case 'WeakSet':
      case 'Error':
        return leftHandOperand === rightHandOperand;
      case 'Arguments':
      case 'Int8Array':
      case 'Uint8Array':
      case 'Uint8ClampedArray':
      case 'Int16Array':
      case 'Uint16Array':
      case 'Int32Array':
      case 'Uint32Array':
      case 'Float32Array':
      case 'Float64Array':
      case 'Array':
        return iterableEqual(leftHandOperand, rightHandOperand, options);
      case 'RegExp':
        return regexpEqual(leftHandOperand, rightHandOperand);
      case 'Generator':
        return generatorEqual(leftHandOperand, rightHandOperand, options);
      case 'DataView':
        return iterableEqual(new Uint8Array(leftHandOperand.buffer), new Uint8Array(rightHandOperand.buffer), options);
      case 'ArrayBuffer':
        return iterableEqual(new Uint8Array(leftHandOperand), new Uint8Array(rightHandOperand), options);
      case 'Set':
        return entriesEqual(leftHandOperand, rightHandOperand, options);
      case 'Map':
        return entriesEqual(leftHandOperand, rightHandOperand, options);
      default:
        return objectEqual(leftHandOperand, rightHandOperand, options);
    }
  }

  /*!
   * Compare two Regular Expressions for equality.
   *
   * @param {RegExp} leftHandOperand
   * @param {RegExp} rightHandOperand
   * @return {Boolean} result
   */

  function regexpEqual(leftHandOperand, rightHandOperand) {
    return leftHandOperand.toString() === rightHandOperand.toString();
  }

  /*!
   * Compare two Sets/Maps for equality. Faster than other equality functions.
   *
   * @param {Set} leftHandOperand
   * @param {Set} rightHandOperand
   * @param {Object} [options] (Optional)
   * @return {Boolean} result
   */

  function entriesEqual(leftHandOperand, rightHandOperand, options) {
    // IE11 doesn't support Set#entries or Set#@@iterator, so we need manually populate using Set#forEach
    if (leftHandOperand.size !== rightHandOperand.size) {
      return false;
    }
    if (leftHandOperand.size === 0) {
      return true;
    }
    var leftHandItems = [];
    var rightHandItems = [];
    leftHandOperand.forEach(function gatherEntries(key, value) {
      leftHandItems.push([ key, value ]);
    });
    rightHandOperand.forEach(function gatherEntries(key, value) {
      rightHandItems.push([ key, value ]);
    });
    return iterableEqual(leftHandItems.sort(), rightHandItems.sort(), options);
  }

  /*!
   * Simple equality for flat iterable objects such as Arrays, TypedArrays or Node.js buffers.
   *
   * @param {Iterable} leftHandOperand
   * @param {Iterable} rightHandOperand
   * @param {Object} [options] (Optional)
   * @return {Boolean} result
   */

  function iterableEqual(leftHandOperand, rightHandOperand, options) {
    var length = leftHandOperand.length;
    if (length !== rightHandOperand.length) {
      return false;
    }
    if (length === 0) {
      return true;
    }
    var index = -1;
    while (++index < length) {
      if (deepEqual(leftHandOperand[index], rightHandOperand[index], options) === false) {
        return false;
      }
    }
    return true;
  }

  /*!
   * Simple equality for generator objects such as those returned by generator functions.
   *
   * @param {Iterable} leftHandOperand
   * @param {Iterable} rightHandOperand
   * @param {Object} [options] (Optional)
   * @return {Boolean} result
   */

  function generatorEqual(leftHandOperand, rightHandOperand, options) {
    return iterableEqual(getGeneratorEntries(leftHandOperand), getGeneratorEntries(rightHandOperand), options);
  }

  /*!
   * Determine if the given object has an @@iterator function.
   *
   * @param {Object} target
   * @return {Boolean} `true` if the object has an @@iterator function.
   */
  function hasIteratorFunction(target) {
    return typeof Symbol !== 'undefined' &&
      typeof target === 'object' &&
      typeof Symbol.iterator !== 'undefined' &&
      typeof target[Symbol.iterator] === 'function';
  }

  /*!
   * Gets all iterator entries from the given Object. If the Object has no @@iterator function, returns an empty array.
   * This will consume the iterator - which could have side effects depending on the @@iterator implementation.
   *
   * @param {Object} target
   * @returns {Array} an array of entries from the @@iterator function
   */
  function getIteratorEntries(target) {
    if (hasIteratorFunction(target)) {
      try {
        return getGeneratorEntries(target[Symbol.iterator]());
      } catch (iteratorError) {
        return [];
      }
    }
    return [];
  }

  /*!
   * Gets all entries from a Generator. This will consume the generator - which could have side effects.
   *
   * @param {Generator} target
   * @returns {Array} an array of entries from the Generator.
   */
  function getGeneratorEntries(generator) {
    var generatorResult = generator.next();
    var accumulator = [ generatorResult.value ];
    while (generatorResult.done === false) {
      generatorResult = generator.next();
      accumulator.push(generatorResult.value);
    }
    return accumulator;
  }

  /*!
   * Gets all own and inherited enumerable keys from a target.
   *
   * @param {Object} target
   * @returns {Array} an array of own and inherited enumerable keys from the target.
   */
  function getEnumerableKeys(target) {
    var keys = [];
    for (var key in target) {
      keys.push(key);
    }
    return keys;
  }

  /*!
   * Determines if two objects have matching values, given a set of keys. Defers to deepEqual for the equality check of
   * each key. If any value of the given key is not equal, the function will return false (early).
   *
   * @param {Mixed} leftHandOperand
   * @param {Mixed} rightHandOperand
   * @param {Array} keys An array of keys to compare the values of leftHandOperand and rightHandOperand against
   * @param {Object} [options] (Optional)
   * @return {Boolean} result
   */
  function keysEqual(leftHandOperand, rightHandOperand, keys, options) {
    var length = keys.length;
    if (length === 0) {
      return true;
    }
    for (var i = 0; i < length; i += 1) {
      if (deepEqual(leftHandOperand[keys[i]], rightHandOperand[keys[i]], options) === false) {
        return false;
      }
    }
    return true;
  }

  /*!
   * Recursively check the equality of two Objects. Once basic sameness has been established it will defer to `deepEqual`
   * for each enumerable key in the object.
   *
   * @param {Mixed} leftHandOperand
   * @param {Mixed} rightHandOperand
   * @param {Object} [options] (Optional)
   * @return {Boolean} result
   */

  function objectEqual(leftHandOperand, rightHandOperand, options) {
    var leftHandKeys = getEnumerableKeys(leftHandOperand);
    var rightHandKeys = getEnumerableKeys(rightHandOperand);
    if (leftHandKeys.length && leftHandKeys.length === rightHandKeys.length) {
      leftHandKeys.sort();
      rightHandKeys.sort();
      if (iterableEqual(leftHandKeys, rightHandKeys) === false) {
        return false;
      }
      return keysEqual(leftHandOperand, rightHandOperand, leftHandKeys, options);
    }

    var leftHandEntries = getIteratorEntries(leftHandOperand);
    var rightHandEntries = getIteratorEntries(rightHandOperand);
    if (leftHandEntries.length && leftHandEntries.length === rightHandEntries.length) {
      leftHandEntries.sort();
      rightHandEntries.sort();
      return iterableEqual(leftHandEntries, rightHandEntries, options);
    }

    if (leftHandKeys.length === 0 &&
        leftHandEntries.length === 0 &&
        rightHandKeys.length === 0 &&
        rightHandEntries.length === 0) {
      return true;
    }

    return false;
  }

  /*!
   * Returns true if the argument is a primitive.
   *
   * This intentionally returns true for all objects that can be compared by reference,
   * including functions and symbols.
   *
   * @param {Mixed} value
   * @return {Boolean} result
   */
  function isPrimitive(value) {
    return value === null || typeof value !== 'object';
  }

  },{"type-detect":38}],36:[function(require,module,exports){
  'use strict';

  /* !
   * Chai - getFuncName utility
   * Copyright(c) 2012-2016 Jake Luer <jake@alogicalparadox.com>
   * MIT Licensed
   */

  /**
   * ### .getFuncName(constructorFn)
   *
   * Returns the name of a function.
   * When a non-function instance is passed, returns `null`.
   * This also includes a polyfill function if `aFunc.name` is not defined.
   *
   * @name getFuncName
   * @param {Function} funct
   * @namespace Utils
   * @api public
   */

  var toString = Function.prototype.toString;
  var functionNameMatch = /\s*function(?:\s|\s*\/\*[^(?:*\/)]+\*\/\s*)*([^\s\(\/]+)/;
  function getFuncName(aFunc) {
    if (typeof aFunc !== 'function') {
      return null;
    }

    var name = '';
    if (typeof Function.prototype.name === 'undefined' && typeof aFunc.name === 'undefined') {
      // Here we run a polyfill if Function does not support the `name` property and if aFunc.name is not defined
      var match = toString.call(aFunc).match(functionNameMatch);
      if (match) {
        name = match[1];
      }
    } else {
      // If we've got a `name` property we just use it
      name = aFunc.name;
    }

    return name;
  }

  module.exports = getFuncName;

  },{}],37:[function(require,module,exports){
  'use strict';

  /* !
   * Chai - pathval utility
   * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
   * @see https://github.com/logicalparadox/filtr
   * MIT Licensed
   */

  /**
   * ### .hasProperty(object, name)
   *
   * This allows checking whether an object has own
   * or inherited from prototype chain named property.
   *
   * Basically does the same thing as the `in`
   * operator but works properly with null/undefined values
   * and other primitives.
   *
   *     var obj = {
   *         arr: ['a', 'b', 'c']
   *       , str: 'Hello'
   *     }
   *
   * The following would be the results.
   *
   *     hasProperty(obj, 'str');  // true
   *     hasProperty(obj, 'constructor');  // true
   *     hasProperty(obj, 'bar');  // false
   *
   *     hasProperty(obj.str, 'length'); // true
   *     hasProperty(obj.str, 1);  // true
   *     hasProperty(obj.str, 5);  // false
   *
   *     hasProperty(obj.arr, 'length');  // true
   *     hasProperty(obj.arr, 2);  // true
   *     hasProperty(obj.arr, 3);  // false
   *
   * @param {Object} object
   * @param {String|Symbol} name
   * @returns {Boolean} whether it exists
   * @namespace Utils
   * @name hasProperty
   * @api public
   */

  function hasProperty(obj, name) {
    if (typeof obj === 'undefined' || obj === null) {
      return false;
    }

    // The `in` operator does not work with primitives.
    return name in Object(obj);
  }

  /* !
   * ## parsePath(path)
   *
   * Helper function used to parse string object
   * paths. Use in conjunction with `internalGetPathValue`.
   *
   *      var parsed = parsePath('myobject.property.subprop');
   *
   * ### Paths:
   *
   * * Can be infinitely deep and nested.
   * * Arrays are also valid using the formal `myobject.document[3].property`.
   * * Literal dots and brackets (not delimiter) must be backslash-escaped.
   *
   * @param {String} path
   * @returns {Object} parsed
   * @api private
   */

  function parsePath(path) {
    var str = path.replace(/([^\\])\[/g, '$1.[');
    var parts = str.match(/(\\\.|[^.]+?)+/g);
    return parts.map(function mapMatches(value) {
      var regexp = /^\[(\d+)\]$/;
      var mArr = regexp.exec(value);
      var parsed = null;
      if (mArr) {
        parsed = { i: parseFloat(mArr[1]) };
      } else {
        parsed = { p: value.replace(/\\([.\[\]])/g, '$1') };
      }

      return parsed;
    });
  }

  /* !
   * ## internalGetPathValue(obj, parsed[, pathDepth])
   *
   * Helper companion function for `.parsePath` that returns
   * the value located at the parsed address.
   *
   *      var value = getPathValue(obj, parsed);
   *
   * @param {Object} object to search against
   * @param {Object} parsed definition from `parsePath`.
   * @param {Number} depth (nesting level) of the property we want to retrieve
   * @returns {Object|Undefined} value
   * @api private
   */

  function internalGetPathValue(obj, parsed, pathDepth) {
    var temporaryValue = obj;
    var res = null;
    pathDepth = (typeof pathDepth === 'undefined' ? parsed.length : pathDepth);

    for (var i = 0; i < pathDepth; i++) {
      var part = parsed[i];
      if (temporaryValue) {
        if (typeof part.p === 'undefined') {
          temporaryValue = temporaryValue[part.i];
        } else {
          temporaryValue = temporaryValue[part.p];
        }

        if (i === (pathDepth - 1)) {
          res = temporaryValue;
        }
      }
    }

    return res;
  }

  /* !
   * ## internalSetPathValue(obj, value, parsed)
   *
   * Companion function for `parsePath` that sets
   * the value located at a parsed address.
   *
   *  internalSetPathValue(obj, 'value', parsed);
   *
   * @param {Object} object to search and define on
   * @param {*} value to use upon set
   * @param {Object} parsed definition from `parsePath`
   * @api private
   */

  function internalSetPathValue(obj, val, parsed) {
    var tempObj = obj;
    var pathDepth = parsed.length;
    var part = null;
    // Here we iterate through every part of the path
    for (var i = 0; i < pathDepth; i++) {
      var propName = null;
      var propVal = null;
      part = parsed[i];

      // If it's the last part of the path, we set the 'propName' value with the property name
      if (i === (pathDepth - 1)) {
        propName = typeof part.p === 'undefined' ? part.i : part.p;
        // Now we set the property with the name held by 'propName' on object with the desired val
        tempObj[propName] = val;
      } else if (typeof part.p !== 'undefined' && tempObj[part.p]) {
        tempObj = tempObj[part.p];
      } else if (typeof part.i !== 'undefined' && tempObj[part.i]) {
        tempObj = tempObj[part.i];
      } else {
        // If the obj doesn't have the property we create one with that name to define it
        var next = parsed[i + 1];
        // Here we set the name of the property which will be defined
        propName = typeof part.p === 'undefined' ? part.i : part.p;
        // Here we decide if this property will be an array or a new object
        propVal = typeof next.p === 'undefined' ? [] : {};
        tempObj[propName] = propVal;
        tempObj = tempObj[propName];
      }
    }
  }

  /**
   * ### .getPathInfo(object, path)
   *
   * This allows the retrieval of property info in an
   * object given a string path.
   *
   * The path info consists of an object with the
   * following properties:
   *
   * * parent - The parent object of the property referenced by `path`
   * * name - The name of the final property, a number if it was an array indexer
   * * value - The value of the property, if it exists, otherwise `undefined`
   * * exists - Whether the property exists or not
   *
   * @param {Object} object
   * @param {String} path
   * @returns {Object} info
   * @namespace Utils
   * @name getPathInfo
   * @api public
   */

  function getPathInfo(obj, path) {
    var parsed = parsePath(path);
    var last = parsed[parsed.length - 1];
    var info = {
      parent: parsed.length > 1 ? internalGetPathValue(obj, parsed, parsed.length - 1) : obj,
      name: last.p || last.i,
      value: internalGetPathValue(obj, parsed),
    };
    info.exists = hasProperty(info.parent, info.name);

    return info;
  }

  /**
   * ### .getPathValue(object, path)
   *
   * This allows the retrieval of values in an
   * object given a string path.
   *
   *     var obj = {
   *         prop1: {
   *             arr: ['a', 'b', 'c']
   *           , str: 'Hello'
   *         }
   *       , prop2: {
   *             arr: [ { nested: 'Universe' } ]
   *           , str: 'Hello again!'
   *         }
   *     }
   *
   * The following would be the results.
   *
   *     getPathValue(obj, 'prop1.str'); // Hello
   *     getPathValue(obj, 'prop1.att[2]'); // b
   *     getPathValue(obj, 'prop2.arr[0].nested'); // Universe
   *
   * @param {Object} object
   * @param {String} path
   * @returns {Object} value or `undefined`
   * @namespace Utils
   * @name getPathValue
   * @api public
   */

  function getPathValue(obj, path) {
    var info = getPathInfo(obj, path);
    return info.value;
  }

  /**
   * ### .setPathValue(object, path, value)
   *
   * Define the value in an object at a given string path.
   *
   * ```js
   * var obj = {
   *     prop1: {
   *         arr: ['a', 'b', 'c']
   *       , str: 'Hello'
   *     }
   *   , prop2: {
   *         arr: [ { nested: 'Universe' } ]
   *       , str: 'Hello again!'
   *     }
   * };
   * ```
   *
   * The following would be acceptable.
   *
   * ```js
   * var properties = require('tea-properties');
   * properties.set(obj, 'prop1.str', 'Hello Universe!');
   * properties.set(obj, 'prop1.arr[2]', 'B');
   * properties.set(obj, 'prop2.arr[0].nested.value', { hello: 'universe' });
   * ```
   *
   * @param {Object} object
   * @param {String} path
   * @param {Mixed} value
   * @api private
   */

  function setPathValue(obj, path, val) {
    var parsed = parsePath(path);
    internalSetPathValue(obj, val, parsed);
    return obj;
  }

  module.exports = {
    hasProperty: hasProperty,
    getPathInfo: getPathInfo,
    getPathValue: getPathValue,
    setPathValue: setPathValue,
  };

  },{}],38:[function(require,module,exports){
  'use strict';

  /* !
   * type-detect
   * Copyright(c) 2013 jake luer <jake@alogicalparadox.com>
   * MIT Licensed
   */
  var promiseExists = typeof Promise === 'function';
  var globalObject = typeof window !== 'undefined' ? window : typeof global !== 'undefined' ? global : self; // eslint-disable-line
  var isDom = 'location' in globalObject && 'document' in globalObject;
  var symbolExists = typeof Symbol !== 'undefined';
  var mapExists = typeof Map !== 'undefined';
  var setExists = typeof Set !== 'undefined';
  var weakMapExists = typeof WeakMap !== 'undefined';
  var weakSetExists = typeof WeakSet !== 'undefined';
  var dataViewExists = typeof DataView !== 'undefined';
  var symbolIteratorExists = symbolExists && typeof Symbol.iterator !== 'undefined';
  var symbolToStringTagExists = symbolExists && typeof Symbol.toStringTag !== 'undefined';
  var setEntriesExists = setExists && typeof Set.prototype.entries === 'function';
  var mapEntriesExists = mapExists && typeof Map.prototype.entries === 'function';
  var setIteratorPrototype = setEntriesExists && Object.getPrototypeOf(new Set().entries());
  var mapIteratorPrototype = mapEntriesExists && Object.getPrototypeOf(new Map().entries());
  var arrayIteratorExists = symbolIteratorExists && typeof Array.prototype[Symbol.iterator] === 'function';
  var arrayIteratorPrototype = arrayIteratorExists && Object.getPrototypeOf([][Symbol.iterator]());
  var stringIteratorExists = symbolIteratorExists && typeof String.prototype[Symbol.iterator] === 'function';
  var stringIteratorPrototype = stringIteratorExists && Object.getPrototypeOf(''[Symbol.iterator]());
  var toStringLeftSliceLength = 8;
  var toStringRightSliceLength = -1;
  /**
   * ### typeOf (obj)
   *
   * Uses `Object.prototype.toString` to determine the type of an object,
   * normalising behaviour across engine versions & well optimised.
   *
   * @param {Mixed} object
   * @return {String} object type
   * @api public
   */
  module.exports = function typeDetect(obj) {
    /* ! Speed optimisation
     * Pre:
     *   string literal     x 3,039,035 ops/sec ±1.62% (78 runs sampled)
     *   boolean literal    x 1,424,138 ops/sec ±4.54% (75 runs sampled)
     *   number literal     x 1,653,153 ops/sec ±1.91% (82 runs sampled)
     *   undefined          x 9,978,660 ops/sec ±1.92% (75 runs sampled)
     *   function           x 2,556,769 ops/sec ±1.73% (77 runs sampled)
     * Post:
     *   string literal     x 38,564,796 ops/sec ±1.15% (79 runs sampled)
     *   boolean literal    x 31,148,940 ops/sec ±1.10% (79 runs sampled)
     *   number literal     x 32,679,330 ops/sec ±1.90% (78 runs sampled)
     *   undefined          x 32,363,368 ops/sec ±1.07% (82 runs sampled)
     *   function           x 31,296,870 ops/sec ±0.96% (83 runs sampled)
     */
    var typeofObj = typeof obj;
    if (typeofObj !== 'object') {
      return typeofObj;
    }

    /* ! Speed optimisation
     * Pre:
     *   null               x 28,645,765 ops/sec ±1.17% (82 runs sampled)
     * Post:
     *   null               x 36,428,962 ops/sec ±1.37% (84 runs sampled)
     */
    if (obj === null) {
      return 'null';
    }

    /* ! Spec Conformance
     * Test: `Object.prototype.toString.call(window)``
     *  - Node === "[object global]"
     *  - Chrome === "[object global]"
     *  - Firefox === "[object Window]"
     *  - PhantomJS === "[object Window]"
     *  - Safari === "[object Window]"
     *  - IE 11 === "[object Window]"
     *  - IE Edge === "[object Window]"
     * Test: `Object.prototype.toString.call(this)``
     *  - Chrome Worker === "[object global]"
     *  - Firefox Worker === "[object DedicatedWorkerGlobalScope]"
     *  - Safari Worker === "[object DedicatedWorkerGlobalScope]"
     *  - IE 11 Worker === "[object WorkerGlobalScope]"
     *  - IE Edge Worker === "[object WorkerGlobalScope]"
     */
    if (obj === globalObject) {
      return 'global';
    }

    /* ! Speed optimisation
     * Pre:
     *   array literal      x 2,888,352 ops/sec ±0.67% (82 runs sampled)
     * Post:
     *   array literal      x 22,479,650 ops/sec ±0.96% (81 runs sampled)
     */
    if (
      Array.isArray(obj) &&
      (symbolToStringTagExists === false || !(Symbol.toStringTag in obj))
    ) {
      return 'Array';
    }

    if (isDom) {
      /* ! Spec Conformance
       * (https://html.spec.whatwg.org/multipage/browsers.html#location)
       * WhatWG HTML$7.7.3 - The `Location` interface
       * Test: `Object.prototype.toString.call(window.location)``
       *  - IE <=11 === "[object Object]"
       *  - IE Edge <=13 === "[object Object]"
       */
      if (obj === globalObject.location) {
        return 'Location';
      }

      /* ! Spec Conformance
       * (https://html.spec.whatwg.org/#document)
       * WhatWG HTML$3.1.1 - The `Document` object
       * Note: Most browsers currently adher to the W3C DOM Level 2 spec
       *       (https://www.w3.org/TR/DOM-Level-2-HTML/html.html#ID-26809268)
       *       which suggests that browsers should use HTMLTableCellElement for
       *       both TD and TH elements. WhatWG separates these.
       *       WhatWG HTML states:
       *         > For historical reasons, Window objects must also have a
       *         > writable, configurable, non-enumerable property named
       *         > HTMLDocument whose value is the Document interface object.
       * Test: `Object.prototype.toString.call(document)``
       *  - Chrome === "[object HTMLDocument]"
       *  - Firefox === "[object HTMLDocument]"
       *  - Safari === "[object HTMLDocument]"
       *  - IE <=10 === "[object Document]"
       *  - IE 11 === "[object HTMLDocument]"
       *  - IE Edge <=13 === "[object HTMLDocument]"
       */
      if (obj === globalObject.document) {
        return 'Document';
      }

      /* ! Spec Conformance
       * (https://html.spec.whatwg.org/multipage/webappapis.html#mimetypearray)
       * WhatWG HTML$8.6.1.5 - Plugins - Interface MimeTypeArray
       * Test: `Object.prototype.toString.call(navigator.mimeTypes)``
       *  - IE <=10 === "[object MSMimeTypesCollection]"
       */
      if (obj === (globalObject.navigator || {}).mimeTypes) {
        return 'MimeTypeArray';
      }

      /* ! Spec Conformance
       * (https://html.spec.whatwg.org/multipage/webappapis.html#pluginarray)
       * WhatWG HTML$8.6.1.5 - Plugins - Interface PluginArray
       * Test: `Object.prototype.toString.call(navigator.plugins)``
       *  - IE <=10 === "[object MSPluginsCollection]"
       */
      if (obj === (globalObject.navigator || {}).plugins) {
        return 'PluginArray';
      }

      /* ! Spec Conformance
       * (https://html.spec.whatwg.org/multipage/webappapis.html#pluginarray)
       * WhatWG HTML$4.4.4 - The `blockquote` element - Interface `HTMLQuoteElement`
       * Test: `Object.prototype.toString.call(document.createElement('blockquote'))``
       *  - IE <=10 === "[object HTMLBlockElement]"
       */
      if (obj instanceof HTMLElement && obj.tagName === 'BLOCKQUOTE') {
        return 'HTMLQuoteElement';
      }

      /* ! Spec Conformance
       * (https://html.spec.whatwg.org/#htmltabledatacellelement)
       * WhatWG HTML$4.9.9 - The `td` element - Interface `HTMLTableDataCellElement`
       * Note: Most browsers currently adher to the W3C DOM Level 2 spec
       *       (https://www.w3.org/TR/DOM-Level-2-HTML/html.html#ID-82915075)
       *       which suggests that browsers should use HTMLTableCellElement for
       *       both TD and TH elements. WhatWG separates these.
       * Test: Object.prototype.toString.call(document.createElement('td'))
       *  - Chrome === "[object HTMLTableCellElement]"
       *  - Firefox === "[object HTMLTableCellElement]"
       *  - Safari === "[object HTMLTableCellElement]"
       */
      if (obj instanceof HTMLElement && obj.tagName === 'TD') {
        return 'HTMLTableDataCellElement';
      }

      /* ! Spec Conformance
       * (https://html.spec.whatwg.org/#htmltableheadercellelement)
       * WhatWG HTML$4.9.9 - The `td` element - Interface `HTMLTableHeaderCellElement`
       * Note: Most browsers currently adher to the W3C DOM Level 2 spec
       *       (https://www.w3.org/TR/DOM-Level-2-HTML/html.html#ID-82915075)
       *       which suggests that browsers should use HTMLTableCellElement for
       *       both TD and TH elements. WhatWG separates these.
       * Test: Object.prototype.toString.call(document.createElement('th'))
       *  - Chrome === "[object HTMLTableCellElement]"
       *  - Firefox === "[object HTMLTableCellElement]"
       *  - Safari === "[object HTMLTableCellElement]"
       */
      if (obj instanceof HTMLElement && obj.tagName === 'TH') {
        return 'HTMLTableHeaderCellElement';
      }
    }

    /* ! Speed optimisation
    * Pre:
    *   Float64Array       x 625,644 ops/sec ±1.58% (80 runs sampled)
    *   Float32Array       x 1,279,852 ops/sec ±2.91% (77 runs sampled)
    *   Uint32Array        x 1,178,185 ops/sec ±1.95% (83 runs sampled)
    *   Uint16Array        x 1,008,380 ops/sec ±2.25% (80 runs sampled)
    *   Uint8Array         x 1,128,040 ops/sec ±2.11% (81 runs sampled)
    *   Int32Array         x 1,170,119 ops/sec ±2.88% (80 runs sampled)
    *   Int16Array         x 1,176,348 ops/sec ±5.79% (86 runs sampled)
    *   Int8Array          x 1,058,707 ops/sec ±4.94% (77 runs sampled)
    *   Uint8ClampedArray  x 1,110,633 ops/sec ±4.20% (80 runs sampled)
    * Post:
    *   Float64Array       x 7,105,671 ops/sec ±13.47% (64 runs sampled)
    *   Float32Array       x 5,887,912 ops/sec ±1.46% (82 runs sampled)
    *   Uint32Array        x 6,491,661 ops/sec ±1.76% (79 runs sampled)
    *   Uint16Array        x 6,559,795 ops/sec ±1.67% (82 runs sampled)
    *   Uint8Array         x 6,463,966 ops/sec ±1.43% (85 runs sampled)
    *   Int32Array         x 5,641,841 ops/sec ±3.49% (81 runs sampled)
    *   Int16Array         x 6,583,511 ops/sec ±1.98% (80 runs sampled)
    *   Int8Array          x 6,606,078 ops/sec ±1.74% (81 runs sampled)
    *   Uint8ClampedArray  x 6,602,224 ops/sec ±1.77% (83 runs sampled)
    */
    var stringTag = (symbolToStringTagExists && obj[Symbol.toStringTag]);
    if (typeof stringTag === 'string') {
      return stringTag;
    }

    var objPrototype = Object.getPrototypeOf(obj);
    /* ! Speed optimisation
    * Pre:
    *   regex literal      x 1,772,385 ops/sec ±1.85% (77 runs sampled)
    *   regex constructor  x 2,143,634 ops/sec ±2.46% (78 runs sampled)
    * Post:
    *   regex literal      x 3,928,009 ops/sec ±0.65% (78 runs sampled)
    *   regex constructor  x 3,931,108 ops/sec ±0.58% (84 runs sampled)
    */
    if (objPrototype === RegExp.prototype) {
      return 'RegExp';
    }

    /* ! Speed optimisation
    * Pre:
    *   date               x 2,130,074 ops/sec ±4.42% (68 runs sampled)
    * Post:
    *   date               x 3,953,779 ops/sec ±1.35% (77 runs sampled)
    */
    if (objPrototype === Date.prototype) {
      return 'Date';
    }

    /* ! Spec Conformance
     * (http://www.ecma-international.org/ecma-262/6.0/index.html#sec-promise.prototype-@@tostringtag)
     * ES6$25.4.5.4 - Promise.prototype[@@toStringTag] should be "Promise":
     * Test: `Object.prototype.toString.call(Promise.resolve())``
     *  - Chrome <=47 === "[object Object]"
     *  - Edge <=20 === "[object Object]"
     *  - Firefox 29-Latest === "[object Promise]"
     *  - Safari 7.1-Latest === "[object Promise]"
     */
    if (promiseExists && objPrototype === Promise.prototype) {
      return 'Promise';
    }

    /* ! Speed optimisation
    * Pre:
    *   set                x 2,222,186 ops/sec ±1.31% (82 runs sampled)
    * Post:
    *   set                x 4,545,879 ops/sec ±1.13% (83 runs sampled)
    */
    if (setExists && objPrototype === Set.prototype) {
      return 'Set';
    }

    /* ! Speed optimisation
    * Pre:
    *   map                x 2,396,842 ops/sec ±1.59% (81 runs sampled)
    * Post:
    *   map                x 4,183,945 ops/sec ±6.59% (82 runs sampled)
    */
    if (mapExists && objPrototype === Map.prototype) {
      return 'Map';
    }

    /* ! Speed optimisation
    * Pre:
    *   weakset            x 1,323,220 ops/sec ±2.17% (76 runs sampled)
    * Post:
    *   weakset            x 4,237,510 ops/sec ±2.01% (77 runs sampled)
    */
    if (weakSetExists && objPrototype === WeakSet.prototype) {
      return 'WeakSet';
    }

    /* ! Speed optimisation
    * Pre:
    *   weakmap            x 1,500,260 ops/sec ±2.02% (78 runs sampled)
    * Post:
    *   weakmap            x 3,881,384 ops/sec ±1.45% (82 runs sampled)
    */
    if (weakMapExists && objPrototype === WeakMap.prototype) {
      return 'WeakMap';
    }

    /* ! Spec Conformance
     * (http://www.ecma-international.org/ecma-262/6.0/index.html#sec-dataview.prototype-@@tostringtag)
     * ES6$24.2.4.21 - DataView.prototype[@@toStringTag] should be "DataView":
     * Test: `Object.prototype.toString.call(new DataView(new ArrayBuffer(1)))``
     *  - Edge <=13 === "[object Object]"
     */
    if (dataViewExists && objPrototype === DataView.prototype) {
      return 'DataView';
    }

    /* ! Spec Conformance
     * (http://www.ecma-international.org/ecma-262/6.0/index.html#sec-%mapiteratorprototype%-@@tostringtag)
     * ES6$23.1.5.2.2 - %MapIteratorPrototype%[@@toStringTag] should be "Map Iterator":
     * Test: `Object.prototype.toString.call(new Map().entries())``
     *  - Edge <=13 === "[object Object]"
     */
    if (mapExists && objPrototype === mapIteratorPrototype) {
      return 'Map Iterator';
    }

    /* ! Spec Conformance
     * (http://www.ecma-international.org/ecma-262/6.0/index.html#sec-%setiteratorprototype%-@@tostringtag)
     * ES6$23.2.5.2.2 - %SetIteratorPrototype%[@@toStringTag] should be "Set Iterator":
     * Test: `Object.prototype.toString.call(new Set().entries())``
     *  - Edge <=13 === "[object Object]"
     */
    if (setExists && objPrototype === setIteratorPrototype) {
      return 'Set Iterator';
    }

    /* ! Spec Conformance
     * (http://www.ecma-international.org/ecma-262/6.0/index.html#sec-%arrayiteratorprototype%-@@tostringtag)
     * ES6$22.1.5.2.2 - %ArrayIteratorPrototype%[@@toStringTag] should be "Array Iterator":
     * Test: `Object.prototype.toString.call([][Symbol.iterator]())``
     *  - Edge <=13 === "[object Object]"
     */
    if (arrayIteratorExists && objPrototype === arrayIteratorPrototype) {
      return 'Array Iterator';
    }

    /* ! Spec Conformance
     * (http://www.ecma-international.org/ecma-262/6.0/index.html#sec-%stringiteratorprototype%-@@tostringtag)
     * ES6$21.1.5.2.2 - %StringIteratorPrototype%[@@toStringTag] should be "String Iterator":
     * Test: `Object.prototype.toString.call(''[Symbol.iterator]())``
     *  - Edge <=13 === "[object Object]"
     */
    if (stringIteratorExists && objPrototype === stringIteratorPrototype) {
      return 'String Iterator';
    }

    /* ! Speed optimisation
    * Pre:
    *   object from null   x 2,424,320 ops/sec ±1.67% (76 runs sampled)
    * Post:
    *   object from null   x 5,838,000 ops/sec ±0.99% (84 runs sampled)
    */
    if (objPrototype === null) {
      return 'Object';
    }

    return Object
      .prototype
      .toString
      .call(obj)
      .slice(toStringLeftSliceLength, toStringRightSliceLength);
  };

  module.exports.typeDetect = module.exports;

  },{}]},{},[1])(1)
  });